Chas G Newstead BSc FRCP

• Consultant renal physician
• St James? University Hospital
• Honorary senior lecturer
• University of Leeds, Leeds, UK

Finally delex acne purchase betnovate 20 gm line, bones provide ready landmarks as clinicians navigate their way around the human body acne light therapy 20 gm betnovate with amex. Overview of the Skeletal System Although most adults have 206 bones acne 70 betnovate 20 gm free shipping, there is some variation acne juvenil order betnovate 20 gm on line. Occasionally acne 17 year old male cheap betnovate generic, some bones fail to fuse during development acne xl order betnovate 20gm otc, also adding to the total. Of these bones, 80 comprise the upright, central supporting axis of the body, which includes the skull, rib cage, and vertebral column. The other 126 bones make up the bones of the limbs and the pelvic and shoulder area. Rather, bones have a number of surface markings, such as flat or rounded areas that allow for joint formation (called articulations), projections that allow for muscle attachment, and depressions or passages that provide routes for blood vessels and nerves. An axis is a straight line around which a body-such as the earth or the human body-revolves. The appendicular skeleton relates to the appendages of the body, such as the arms and legs. Frontal bone Skull Maxilla Mandible Pectoral Girdle Thoracic Cage Clavicle Scapula Sternum Ribs Costal cartilages Parietal bone Occipital bone Mandible Clavicle Scapula Humerus Vertebral column Os coxae Pelvis Sacrum Coccyx Carpals Metacarpal bones Phalanges Os coxae Ulna Radius Femur Patella Fibula Tibia Tarsals Metatarsal bones Phalanges Anterior view Posterior view 118 Bones of the Skeletal System the axial skeleton consists of 80 bones, and the appendicular skeleton consists of 126 bones. Specifically, the scientists who examine skeletal remains are called forensic anthropologists. The top of this delicate bone, called the cribriform plate, forms part of the roof of the nasal cavity. Tiny perforations in the cribriform plate allow branches of the olfactory nerve to reach the brain. A projection on the cribriform plate provides an attachment for the meninges, the membrane that encloses the brain. A sharp, upward blow can drive bone fragments through the cribriform plate and into the brain. If this happens, cerebrospinal fluid will leak out of the nose; it also opens a pathway for infection into the brain. Traumatic injury to this bone can also shear off the olfactory nerves, resulting in a loss of sense of smell. On top of the sphenoid bone is an indented area called the sella turcica, which houses the pituitary gland. Parietal bone Frontal bone the lambdoid suture is the line of articulation between the parietal bones and the occipital bone. Occipital bone Greater wing of sphenoid bone the squamous suture runs along the top edge of the temporal bone. Temporal bone Anterior Frontal bone Coronal suture the sagittal suture is the joint between the right and left parietal bones. Parietal bone Lambdoid suture Occipital bone Posterior Foramen Magnum the skull contains a number of holes called foramina that allow for passage of nerves and blood vessels. A large opening in the base of the skull, called the foramen magnum, allows the spinal cord to pass through as it connects to the brainstem. Frontal bone Cribriform plate (ethmoid bone) Sphenoid bone Sella turcica Temporal bone Parietal bone Life lesson: Brain swelling Just like any other tissue, when the brain is injured, it swells. If the swelling becomes severe, the increased pressure will force the brainstem down, through the foramen magnum. The restricted opening of the foramen magnum will constrict the brainstem, resulting in respiratory arrest and, usually, death. They support the teeth, provide an attachment point for the muscles used in chewing and for facial expression, form part of the nasal and orbital cavities, and also give each face its unique characteristics. The maxillae (singular: maxilla) form the foundation of the face; every other facial bone (except for the mandible) articulates with the maxillae. The maxillae form part of the floor of the orbits, part of the roof of the mouth, and part of the floor and walls of the nose. Lacrimal bones (2 bones): these paper-thin bones form part of the side wall of the orbit. Nasal bones (2 bones): these rectangular bones form the bridge of the nose; the rest of the nose is shaped by cartilage. Inferior nasal conchae (2 bones): the conchae bones (singular: concha) contribute to the nasal cavity. Palatine bones (2 bones): these bones form the posterior portion of the hard palate, part of the wall of the nasal cavity, and part of the floor of the orbit. Base of skull as viewed from below 122 Bones Associated with the Skull Several other bones are associated with the skull but not considered a part of the skull. Called auditory ossicles, these bones are named the malleus (hammer), incus (anvil), and stapes (stirrup). Hyoid Larynx Sinuses the skull contains several cavities, which include the paranasal sinuses. The four pairs of sinuses-which are named for the bones in which they reside-open into the internal nose. Filled with air, they lighten the skull and act as resonators for sound production. The areas between the unfused bones, which are covered by fibrous membranes, are called fontanels. Frontal bone Coronal suture Parietal bone Lambdoid suture Squamous suture Occipital bone the posterior (occipital) fontanel is the smaller fontanel. For example, suture lines that are abnormally wide suggest hydrocephalus, a condition in which excessive amounts of cerebrospinal fluid accumulate in the brain, causing the cranium to expand. A bulging anterior fontanel signals increased intracranial pressure, such as may occur following a head injury or infection. The normal curves develop as the infant begins to lift his head and, later, as he begins to walk. It usually occurs in adolescent girls, sometimes the result of the vertebrae failing to develop correctly on one side. However, all vertebrae have a number of characteristics in common, as illustrated here. The spinous processes are the bumps you feel when you run your hand along the spine. Lamina An opening called the vertebral foramen allows for passage of the spinal cord. Both the transverse and spinous processes serve as attachment points for muscles and ligaments. Anterior Intervertebral Disc In between each vertebra is a layer of cartilage called an intervertebral disc. The nucleus pulposus can then ooze out from the center of the disc and press on the spinal cord or a spinal nerve, causing pain. In this procedure, both laminae and the spinal processes are removed, which relieves pressure on the spinal nerve. However, the most unique of all the vertebrae are the first two cervical vertebrae (C1 and C2), known as the atlas and the axis, respectively. Depressions on each side of the vertebra articulate with bony projections from the occipital bone of the skull. When the head moves back and forth (such as when nodding "yes"), the projections rock back and forth in these depressions. Axis the C2 vertebra, called the axis, has a projection called the dens, or odontoid process. The dens projects into the atlas and allows the head to swivel from side to side (such as when saying "no. In addition, as bony projections from the occipital bone rock back and forth on the depressions of the atlas, the head can move back and forth. The structure of the vertebrae allows the spine to bend forward further than it can bend backward. Many different muscles, as well as strong ligaments, stabilize the vertebral column while still allowing flexibility and movement. These bones form a cone-shaped cage that surrounds and protects the heart and lungs and provides an attachment point for the pectoral girdle (shoulder) and upper limbs. Expansion and contraction of the thoracic cage causes the pressure changes in the lungs that allow breathing to occur. Ribs 1 to 7, called true ribs, attach to the sternum by a strip of hyaline cartilage called costal cartilage. Costal cartilages Ribs 8, 9, and 10 attach to the cartilage of rib 7; these ribs, as well as ribs 11 and 12, are called false ribs. Pregnancy as well as lung diseases, such as emphysema, cause the angle to increase. Ribs 11 and 12, also called floating ribs, do not attach to any part of the anterior thoracic cage. The two pectoral girdles- one on each side of the body-consist of a clavicle (collarbone) and a scapula (shoulder blade). A slightly S-shaped bone, the clavicle articulates with the sternum and the scapula and helps support the shoulder. Located on the posterior portion of the thorax, the scapula lies over ribs 2 to 7. Upper Limb the upper limb, or arm, consists of the humerus (upper arm bone), the radius and the ulna (the bones of the lower arm), and the carpals (the bones of the hand). One of the two bones of the lower arm, the radius, is located on the same side as the thumb. The styloid processes of the radius and ulna are the bony bumps that can be felt at the wrist. The phalanges are identified by the Roman numerals I through V (beginning with the thumb) and as being proximal, middle, or distal. The proximal end is called the base, the shaft is called the body, and the distal end is called the head. The knuckles that appear when you clench your fist are the heads of the metacarpals. Ulna Radius Eight carpal bones-arranged in two rows of four bones-form the wrist. When someone performs the same motion over and over-even typing on a keyboard-without rest, the muscles in the wrists become fatigued and, eventually, the joint becomes inflamed. Doctors have dubbed an inflammation of the tendons of the wrist as "Guitar Hero syndrome," because it has been occurring in those who have spent many hours strumming to the video game. Another high-tech injury is "BlackBerry thumb": a painful inflammation in the thumb as a result of frequent texting. Moving from left to right in two rows, the bones are scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, and hamate. The os coxae is not a single bone; rather, it consists of three bones fused together, as shown here. Ilium: A large, flaring section you can feel under the skin Ischium: the lower posterior portion Pubis: the most anterior portion that joins with the other pubis at the symphysis pubis, a disc of cartilage that separates the two pubic bones. Sacrum Symphysis pubis Os coxae Posteriorly, each os coxae articulates with the sacrum at the sacroiliac joint. The pelvis supports the trunk, provides an attachment point for the legs, and also protects the organs of the pelvis (including the lower colon, reproductive organs, and urinary bladder). The diameter of the pelvic outlet is measured as the distance between the two ischial bones. The pelvic outlet is the passageway through which an infant enters the world; therefore, the distance between the two ischial bones must be wide enough to allow his head to pass. Pelvic brim the false pelvis extends between the outer, flaring edges of the iliac bones. More importantly, the bones of the lower limb are articulated in such a way as to allow the body to move. Femur the longest and strongest bone in the body, the femur articulates with the acetabulum of the pelvis to form a ball-and-socket joint. Greater trochanter Lesser trochanter the head of the femur fits into the rounded contour of the acetabulum. Shaft Patella Commonly known as the kneecap, the patella is a triangular sesamoid bone embedded in the tendon of the knee. Medial epicondyle Lateral epicondyle the medial and lateral epicondyle are the widest points of the femur at the knee. Tibia Fibula the long and slender fibula resides alongside the tibia and helps stabilize the ankle. Foot and Ankle the bones of the foot and ankle are arranged similarly to those of the hand. The great toe, called the hallux, contains only two bones: a proximal and distal phalanx. The metatarsals-which are numbered I through V, beginning medially-form the middle portion of the foot. The talus articulates with three bones: the calcaneus on its inferior surface, the tibia on its superior surface, and another tarsal bone (called the navicular) on its anterior surface. Arches of the Foot Strong ligaments hold the foot bones together in a way that forms arches in the foot. Just as arches add supporting strength to a building, foot arches give the foot more strength to support the weight of the body. The arches of the foot include a lateral longitudinal arch, a medial longitudinal arch, and a transverse arch.

How do bacteria know they are on a surface and regulate their response to an adhering state Bacterial adhesion to animal tissues: Protein determinants for recognition of extracellular matrix components skin care during pregnancy cheap betnovate online amex. Anchorless adhesins and invasins of Gram-positive bacteria: A new class of virulence factors acne definition order betnovate 20gm otc. Bacterial Adhesion: Molecular and Ecological Diversity (Wiley Series in Ecological and Applied Microbiology) acne treatment home remedies buy cheap betnovate on line. Adhesion acne 5 year old generic 20gm betnovate with amex, invasion and evasion: the many functions of the surface proteins of Staphylococcus aureus skin care shiseido purchase 20gm betnovate overnight delivery. Candida albicans morphogenesis and host defence: discriminating invasion from colonization acne lotion purchase cheapest betnovate. Fibronectin: A multidomain host adhesin targeted by bacterial fibronectin-binding proteins. Bacterial virulence in the moonlight: Multitasking bacterial moonlighting proteins are virulence determinants in infectious disease. Cell adhesion molecules in the pathogenesis of and host defence against microbial infection. Fibronectin-, vitronectin- and laminin-binding proteins at the cell walls of Candida parapsilosis and Candida tropicalis pathogenic yeasts. Mycoplasma pneumoniae cytadherence: Organization and assembly of the attachment organelle. Pili in Gram-positive bacteria: Assembly, involvement in colonization and biofilm development. Vitronectin in bacterial pathogenesis: A host protein used in complement escape and cellular invasion. Human pathogens utilize host extracellular matrix proteins laminin and collagen for adhesion and invasion of the host. Mucosal physical and chemical innate barriers: Lessons from microbial evasion strategies. Teichoic acids and related cell-wall glycopolymers in Gram-positive physiology and host interactions. As described in Chapter 4, the skin and mucosae are often called barrier epithelia because they protect the body from physical and chemical damage, infection, dehydration, and heat loss. The process used by pathogens to cross barrier epithelia is frequently called invasion, but the term invasion implies force on the part of the pathogen, whereas in reality almost all pathogens trick barrier epithelial cells into taking them up. Once pathogens have crossed the barrier epithelia, they can migrate across the endothelium and invade the circulatory and lymphatic systems, causing systemic infections. We will see that the different classes of pathogen, bacteria, fungi, viruses and parasites employ remarkably similar strategies to enter epithelial cells that are the barrier to their invasion of deeper tissue and organs. The infectious cycle of almost all human pathogens begins with attachment and colonisation of the barrier epithelia, as discussed in Chapter 4. In the majority of instances colonization is followed by traversal of the barrier epithelia (skin and mucosae) as the initial phase in local and systemic spread of the agent. The simplest way for pathogens to cross the barrier epithelia is to take advantage of breaches in the integrity of the epithelium caused by trauma. Epithelial damage may be as trivial as a microscopic wound or as severe as a traumatic wound. Surgical wounds or, indeed, the placement of intravascular catheters provides entry directly into the dermis and the circulatory system, by-passing the epithelial barrier. The invasive action of a catheter is replicated in nature by the biting mouthparts of arthropod vectors such as mosquitoes and ticks that penetrate and traverse the skin. Intact skin is a formidable barrier to infectious agents, so the vast majority of pathogens choose to enter the human body via the natural portals of entry: the eyes, nose, mouth, genitourinary tract and anus. The most common routes of entry are the respiratory and the gastrointestinal tracts. The mucosal epithelia function to permit the uptake of nutrients, excretion of waste products and exchange of oxygen and carbon dioxide and in some areas are only a single cell thick. From top to bottom: the blood-brain barrier is made by brain endothelial cells that express tight junctions. The intestinal barrier is a mucosal barrier made by a monolayer of epithelial cells. The placental barrier is constituted by both syncytial trophoblastic cells and mononuclear cytotrophoblasts. Given the large surface area and delicacy of the mucosal epithelium, it is not surprising that the human immune system commits the majority of its innate and adaptive immune resources to their protection in the form of an integrated system known as the mucosal immune system. The surface layers of the skin, the epidermis, are composed of strata of squamous epithelial cells, the outermost of which are dead, keratinised squames. Most of the surface of the skin contains hair follicles, but in humans, the ventral surface of the fingers, palms, soles of the feet, lips, labia minora, and glans penis lack hair. Sebaceous glands are found all over the skin except for the palms of the hands and soles of the feet. The skin surface is protected by a number of mechanisms that include its resident microbiota, an acidic pH (4. It has been estimated that the total surface of the skin is replaced every month by desquamation. In addition, sebum, the secretion of sebaceous glands, contains an array of antimicrobial factors including the muramidase lysozyme that hydrolyses peptidoglycan; various antimicrobial peptides, including dermacidin, psoriasin, Rnase 7, human -defensins 1, 2, and 3 and cathelicidin; fatty acids and the antibody immunoglobulin A. There is no evidence that pathogenic bacteria or viruses are capable of penetrating intact, keratinised, squamous epithelium. Rather, they breach the skin via hair follicles, sweat glands, or sites of microscopic or macroscopic damage. Certain eukaryotic pathogens can penetrate intact, keratinised, squamous epithelium and use hydrolytic enzymes to do so. However, given the opportunity, these organisms take advantage of natural (or otherwise) breaches in the skin. Because the mucosal epithelia is not keratinised (except for the gingivae, hard palate and dorsum of the tongue) and is but a single cell thick in some areas, organisms capable of digesting intact skin are likely able to digest intact mucosal epithelium too. Enzymatic degradation Many microorganisms both saprophytes and parasites secrete degradative enzymes such as proteases, lipases and glycosidases. These hydrolytic enzymes function to acquire nutrients from the environment and, in the case of human parasites, to break down tissues. Three major groups of fungi, Candida albicans, the dermatophytes (Epidermophyton species, Trichophyton species, and Microsporum species) and Malassezia species are capable of infecting and destroying skin, nails and hair shafts. These fungi produce a variety of hydrolytic enzymes including lipases, phospholipases, acid proteases, elastase, and keratinases. In the case of protozoan, nematode, trematode, and cestode parasites, the larvae of the nematodes Anclostoma duodenale, Necator americanus and Stronglyoides stercoralsis can penetrate intact skin as well as enter through hair follicles or cracks in the skin. The ability to invade intact skin by these larvae is thought to be mediated by hydrolytic enzymes. These larvae produce all of the known classes of proteases and can degrade collagen, fibronectin, laminin, elastin and hyaluronic acid. Trophozoites of the pathogenic and opportunistic free-living amoebae, Acanthamoeba species and Balamuthia mandrillaris, appear to have the capacity to invade intact skin as well as intact mucus membranes. Again, they secrete hydrolytic enzymes that include phospholipases, serine and cysteine proteases, and metalloproteases. Several different lipases are produced by members of the bacterial genus Staphylococcus. M cells take up and transcytose microorganisms as well as food and macromolecules. Transcytosis is a type of endocytosis in which macromolecules and particles are internalised in vesicles on one side of a cell and discharged on the other side. Several bacteria such as Yersinia enterocolitica, Shigella flexneri and Salmonella enterica serovar typhi and S. In addition to M cells, there are dCs in the lamina propria of mucosal epithelia that extend fingers of cytoplasm (dendrites) between enterocytes (intestinal epithelial cells) and into the lumen of the gut where they can sample food and microorganisms. Pathogens entering the sub-epithelial tissues are engulfed and destroyed by resident phagocytic cells such as macrophages. These cells, called sentinel cells, together with the epithelium itself, alert the adaptive immune system to the presence and nature of pathogens. Phagocytosis is the major mechanism by which the host destroys and clears invading pathogens, but some pathogens are able to utilise phagocytosis to facilitate their spread. They are able to do this because they have devised mechanisms to avoid destruction in the phagolysosome of these cells and use the phagocyte as a Trojan horse. Trichomonas vaginalis employs cysteine proteases in the enzymatic destruction of vaginal, cervical and prostatic epithelium. The intermediate flagellate form of Naegleria fowleri enters its human host via the olfactory neuroepithelium. Trichinella spiralis and Dracunculus medinensis can invade the small intestine presumably by enzymatic degradation as both have been shown to possess metallo- and serine proteases. The larvae of the flukes Fasciola hepatica, Opisthorchis sinensis and Paragonimus westermani invade the duodenum utilising proteolytic enzymes including cathepsin l, cathepsin B, asparaginyl endopeptidase, cysteine proteases, trypsin-like serine proteases and carboxypeptidases. It is likely that the larval forms of the nematode Ascaris lumbricoides, various Toxocara species and Baylisacaris procyonis penetrate the mucosal epithelium of the small intestines by employing secreted degradative enzymes. Moving junction Apicomplexan parasites are a large group of protozoans that are characterised by having a special organelle called an apical complex. Most of the apicomplexa are single-celled and spore-forming and include the human pathogens Babesia species, Plasmodium species, Cryptosporidium parvum, Cyclospora cayetanensis, Isospora belli, and Toxoplasma gondii. Although these parasites enter different types of host cells, they employ the same method of host cell entry. The host cell membrane invaginates in response to the forward movement of the parasite, which becomes progressively internalised in a vacuole termed the parasitophorous vacuole. A common feature of apicomplexan protozoa is the presence at their apex of secretory organelles termed micronemes and rhoptries. Proteins secreted from these organelles are involved in parasite adhesion, motility and internalization. Paracytosis Paracytosis is the term given to the mechanism by which microorganisms cross the barrier epithelia via the tight intercellular junctions that seal adjacent epithelial cells together. The most apical is the tight junction below which are the adherens junction, desmosomes and gap junctions. The first three comprise the apical junction complex and consist of transmembrane proteins coupled to cytoplasmic adaptors and the actin cytoskeleton. Transmembrane proteins of tight junctions are the junction components most vulnerable to pathogenic microorganisms when they contact the mucosal epithelium because they are the most apically located. It remains unclear whether this constriction is the result of forces generated by the host cytoskeleton, which the parasite must displace to enter the cell, or by internal forces generated by the operation of the actin/myosin motors that power invasion at the site of entry. These bacteria induce a Toll-like receptor (TlR)-dependent down-regulation of claudins 7 and 10. Claudins are tight junction components key to the maintenance of epithelial barrier integrity and their down-regulation compromises the integrity of the tight junction, allowing ingress of these bacteria. The principal role of these effectors is to manipulate the actin cytoskeleton to promote uptake by endocytosis. The secretion systems of gram-negative and gram-positive bacteria are described later in this chapter. One effect of the bacterial proteins injected by secretion systems can be the disruption of intercellular tight junctions. Clostridium perfringens is an anaerobic gram-positive spore-forming rod that causes necrotising infections of muscle but also an acute, generally mild form of food poisoning. The enterotoxin is released from the bacterium during its transition from vegetative cell to spore in the small intestine and binds to claudins 3 and 4 in the tight junction between enterocytes impairing their integrity. Reoviruses and rotaviruses use protein components of the tight junction as their ligands for cell entry. Several pathogenic fungi, including Candida albicans, can traverse epithelial barriers by proteolytic degradation of intercellular tight junctions. It has been suggested that Entamoeba histolytica and Toxoplasma gondii may cross the epithelium via paracytosis based on the observation that they collect at epithelial intercellular junctions. Endocytosis Endocytosis is a type of energy-requiring active transport by which cells take up molecules and particles into their cytoplasm by engulfing them. There are five different types of endocytosis: macropinocytosis, caveolae-mediated endocytosis, clathrin-mediated endocytosis, clathrin-independent endocytosis and phagocytosis. All involve reorganisation of the actin cytoskeleton and intersection with a common endosomal network. We will briefly consider the different forms of endocytosis with the exception of phagocytosis, which is a specialised type of endocytosis performed by professional phagocytic cells such as neutrophils, monocyte/macrophages and dCs. Macropinocytosis: Macropinocytosis occurs in response to growth factors or, in the case of antigen-presenting cells, it is a constitutive process. It is a mechanism by which cells sample soluble molecules and particulates in their surroundings. The macropinosomes pinch off from the plasma membrane and traffic deeper into the cell where they enter the endocytic pathway and fuse with lysosomes. Caveola-mediated endocytosis: Caveolae are a specialised type of lipid raft that forms sub-microscopic, plasma membrane pits consisting of a family of cell membrane proteins called caveolins of which there are three members (caveolin 1, 2 and 3). Caveolin oligomerisation is necessary for formation of caveolar endocytic vesicles. Content of the macropinosomes are then either degraded at the late endosome/lysosome or recycled back to the plasma membrane. Caveolae have various functions that include protection of cells from mechanical stress given that they can act as mechanosensors and in cell signalling and lipid regulation.

Emphysema develops very gradually acne 6 year old buy cheap betnovate 20 gm on-line, usually after years of exposure to cigarette smoke skin care 20s betnovate 20gm amex. Air pollution or certain occupations (such as welding acne xylitol buy betnovate 20 gm fast delivery, mining acne topical medications quality betnovate 20gm, or working near asbestos) can also be contributing factors acne y embarazo buy cheapest betnovate. This information is usually obtained by having the person breathe through a device called a spirometer acne moisturizer order betnovate 20gm amex. This amount of air-inhaled using maximum effort after a normal inspiration-is called the inspiratory reserve volume. The amount of air that can be exhaled after a normal expiration by using maximum effort is the expiratory reserve volume. Called the residual volume, this air ensures that gas exchange continues even between breaths. The amount of air that can be inhaled and exhaled with the deepest possible breath is the vital capacity. The air is said to be in the anatomical dead space: in the passageways instead of the alveoli. Physiological dead space includes all the air in conducting airways (the anatomical dead space) plus the air in any alveoli that are poorly perfused and, therefore, less efficient in gas exchange. Certain diseases cause portions of the lung to be poorly perfused, leading to increased physiological dead space. In general, a tall person has larger lungs, and therefore a larger vital capacity, than does a short person. Also, standing erect increases vital capacity, whereas slouching or lying down decreases it. For example, excess fluid in the abdomen or pleura encroaches on the space occupied by the lungs, diminishing vital capacity. Congestive heart failure causes blood to back up in the lungs, filling alveolar air space and decreasing vital capacity. On the other hand, exercise programs and yoga have been shown to help increase vital capacity. Variations in Respiratory Rhythm A variety of conditions, including exercise, anxiety, and various disease states, influence respiratory rate and rhythm. This extra load reduces all lung volumes, thus interfering with optimal respiratory function. This exchange of gases-both in the lungs and the tissues of the body-depends on differences in pressure. The air we breathe has a pressure of 760 mm Hg; this is known as total atmospheric pressure. The atmosphere consists of about 78% nitrogen, 21% oxygen, and about 1% other gases, of which 0. The contribution of a single gas in any mixture of gases is called partial pressure. That Makes Sense the partial pressure of a gas directly relates to its concentration in a mixture. The maneuver uses the residual volume of air already in the lungs to expel an object in the trachea. Wrap your other arm around the person from the other side, placing your other hand over your fist. The key point to remember is that gas diffuses from an area of higher pressure to an area of lower pressure until the pressures are equalized. Follow the path of blood along the circulatory route, noting the differences in the partial pressures of oxygen and carbon dioxide. The ratio between the amount of air flowing into the alveolus (ventilation) and the flow of blood through the capillaries (perfusion) is known as ventilation-perfusion coupling. This redirects blood to better ventilated alveoli, where blood cells can upload oxygen. In contrast: If a portion of the lung has good airflow, oxygen levels in those blood vessels rise. In turn, blood flow to that area increases, providing more blood cells to take up the abundance of available oxygen. When systemic arteries experience a lack of oxygen, vessels dilate to allow more blood to flow into the area. The goal is the same: Ensuring that organs and tissues receive an adequate supply of oxygen. In the lungs, this occurs when available blood flow changes to allow blood cells to take up oxygen. Systemically, this occurs when blood flow changes to allow the delivery of oxygen to areas that need it most. Factors Affecting Gas Exchange Optimal gas exchange depends on numerous factors, including those listed in the table below. Factor Potential Disruption O2 Bronchiole Adequate airway A foreign body, tumor, or obstruction can block the flow of air in an airway. Also, certain diseases (such as emphysema, chronic bronchitis, or asthma) can narrow airways, limiting airflow. Adequate alveolar surface area Some disorders (such as pneumonia, pulmonary edema, or right-sided heart failure) can cause the alveoli to fill with something other than air (such as fluid, pus, or blood). Other disorders (such as emphysema, pneumothorax, and surfactant disorders) decrease the functional surface area of the lung, making less area for gas diffusion, and blood oxygen levels decline. At high altitudes, the partial pressure of oxygen in inspired air is less than at sea level. Adequate blood supply A diminished supply of blood to the alveoli (such as from a pulmonary embolism) means that fewer blood cells are available to take up oxygen. Once there, the difference in pH between the arterial and venous blood is enough to break the bond between the oxygen and the hemoglobin. The number of oxygen molecules hemoglobin takes up-referred to as oxygen saturation-varies, depending on the amount of oxygen dissolved in the surrounding fluid (the partial pressure of oxygen). In the lungs, where the partial pressure of oxygen is high, oxygen binds readily to available hemoglobin. A tool for understanding how hemoglobin binds with and releases oxygen is the oxyhemoglobin dissociation curve. The oxyhemoglobin dissociation curve (shown below) displays the relationship between the partial pressure of oxygen and oxygen saturation. As soon as the first heme molecule binds with the first molecule of oxygen, hemoglobin changes shape in a way that facilitates the uptake of the second oxygen molecule by another heme group. Conversely, lowered temperature and increased pH decrease unloading, which shifts the curve to the left. Life lesson: Aging and the respiratory system As the body ages, numerous changes occur in the respiratory system-all leading to a general reduction in respiratory efficiency. Older adults are also less capable of clearing irritants and mucus from the lungs, increasing their risk for developing pneumonia after a bacterial or viral illness. Which structure is responsible for directing food and liquids into the esophagus during swallowing Inhaled food or foreign objects are most likely to lodge in which part of the respiratory system Lubricate the pleural surfaces to allow them to glide painlessly during lung expansion and contraction b. Identify the mechanisms used by the kidneys to ensure a steady glomerular filtration rate. Discuss the tubular reabsorption and secretion that occurs in the different parts of the renal tubule. Cleansing the blood of these toxic substances is the job of the kidneys-the principal organs of the urinary system. As blood filters through the kidneys, these mighty organs remove potential poisons, adjust the water content of blood, tweak levels of sodium and potassium, and adjust the pH level. Overview of the Urinary System the urinary system consists of the kidneys, ureters, urinary bladder, and urethra. They are also retroperitoneal, meaning that they are posterior to the parietal peritoneum. The ribs offer some protection to the kidneys, as does a heavy cushion of fat encasing each organ. The interior of the kidney consists of two regions: the renal cortex (the site of urine production) and the renal medulla (the site of urine collection). Extensions from the renal cortex, called renal columns, divide the interior region into cone-shaped sections. Consisting of tubules for transporting urine away from the cortex, the base of each pyramid faces outward toward the cortex. The major calyces converge to form the renal pelvis, which receives urine from the major calyces. The renal pelvis continues as the ureter, a tube-like structure that channels urine to the urinary bladder. Fibrous capsule Structures (such as blood vessels, the ureters, and nerves) enter and leave the kidney through a slit called the hilum-located in a concave notch on the medial side. As it enters the kidney, the renal artery divides, branching into smaller and smaller arteries. Blood eventually leaves the kidney through the renal vein, which empties into the inferior vena cava. Cortex the efferent arteriole leads to a network of capillaries around the renal tubules called peritubular capillaries. Medulla Collecting duct 5 Blood flows from the peritubular capillaries into larger and larger veins that eventually feed into the renal vein. Loop of Henle 394 Renal Innervation Along with blood vessels, nerves also enter the kidney at the hilum. These mainly sympathetic fibers stimulate the afferent and efferent arterioles, controlling the diameter of the vessels, which, in turn, regulate the rate of urine formation. Also, if blood pressure drops, the nerves stimulate the release of renin, an enzyme that triggers processes for restoring blood pressure. These tiny structures consist of two main components: a renal corpuscle-which filters blood plasma-and a renal tubule- where urine is formed. From there, it flows into the proximal renal tubule on the other side of the capsule. Proximal tubule Renal Tubule Leading away from the glomerulus are a series of tube-like structures that, collectively, are called the renal tubule. The renal tubule can be divided into four regions: the proximal convoluted tubule, nephron loop, distal convoluted tubule, and collecting duct. The renal tubule has been stretched out in the following figure to more clearly show the different regions. Afferent arteriole Efferent arteriole Blood flow Renal corpuscle 3 After returning to the cortex, the ascending limb coils again, forming the distal convoluted tubule. Thousands of microvilli that allow absorption to occur line the inside of the proximal convoluted tubule. This entire segment-which consists of a descending limb and an ascending limb-is called the loop of Henle. The collecting duct receives drainage from the distal convoluted tubules of several different nephrons. The collecting duct passes into a renal pyramid, where it merges with other collecting ducts to form one tube. The loop of Henle dips into the renal medulla; some dip in only slightly whereas others extend deep into the medulla. Filtration in the glomerulus occurs for the same reason filtration occurs in other blood capillaries: the existence of a pressure gradient. Consequently, blood flows in faster than it can leave, which contributes to higher pressure within the glomerular capillaries. Blood cells and most plasma proteins, however, are too large to pass through the pores. The body reabsorbs about 99% of this filtrate, leaving 1 to 2 liters to be excreted as urine. The presence of protein in the urine-typically an abnormal finding-is called proteinuria. In this instance, researchers think the proteinuria may result because hormones released during exercise temporarily alter the permeability of the filtration membrane. Life lesson: Hypertension and kidney damage A common cause of kidney damage and kidney failure is uncontrolled hypertension. Hypertension also causes atherosclerosis in blood vessels throughout the body, including those in the kidneys. The kidneys employ various mechanisms to control blood flow and ensure a steady glomerular filtration rate. For example, rising blood pressure stimulates the afferent arterioles to contract, preventing a surge of blood into the glomerulus. Finally, a key mechanism for maintaining blood pressure and, therefore, a steady glomerular filtration rate, is the renin-angiotensin-aldosterone system. Specialized cells found primarily in the afferent arterioles-called juxtaglomerular cells-respond by releasing the enzyme renin. In this situation, the glomerular filtration rate may slow to only a few milliliters per minute.

In general acne nodules betnovate 20 gm visa, neurotransmitters can be classified into one of two categories: small-molecule neurotransmitters (which trigger rapid synaptic actions) and neuropeptides (which modulate slower skin care experts discount betnovate on line, ongoing synaptic functions) skin care mario badescu purchase discount betnovate line. Abnormalities of neurotransmitter function contribute to a wide range of neurological and psychiatric disorders - purchase betnovate 20gm without a prescription. Some common neurotransmitters include acetylcholine skin care kemayoran cheap betnovate 20 gm, epinephrine acne essential oil recipe discount generic betnovate canada, norepinephrine, serotonin, dopamine, and histamine. In fact, in a particular portion of the brain, one neuron can have up to 100,000 synapses. Thirty-one pairs of spinal nerves branch out from the spinal cord, linking it to the far reaches of the body. Although the spinal cord is part of the central nervous system and the peripheral nerves are part of the peripheral nervous system, the two are inseparable. Nerves from the cervical region of the spinal cord innervate the chest, head, neck, shoulders, arms, hands, and diaphragm. Basically a bundle of nerve fibers, the spinal cord extends from the base of the brain until about the first lumbar vertebra. Nerves from the thoracic region extend to the intercostal muscles of the ribcage, the abdominal muscles, and the back muscles. The lumbar spinal nerves innervate the lower abdominal wall and parts of the thighs and legs. Nerves from the sacral region extend to the thighs, buttocks, skin of the legs and feet, and anal and genital regions. However, the vertebral column grows faster than the spinal cord and, by the time a baby is born, the spinal cord ends at about the level of L3. This explains why lumbar punctures (procedures in which a needle is inserted into spinal canal to withdraw cerebrospinal fluid for analysis) are performed between L3 and L4. A cross section clearly shows the two types of nervous tissue (white matter and gray matter) that make up the spinal cord. Gray matter-which appears gray because of its lack of myelin- contains mostly the cells bodies of motor neurons and interneurons. This H-shaped mass is divided into two sets of horns: the posterior (dorsal) horns and the ventral (anterior) horns. It contains bundles of axons (called tracts) that carry impulses from one part of the nervous system to another. Vertebral body A minute opening called the central canal carries cerebrospinal fluid through the spinal cord. Attachment of Spinal Nerves Spinal nerves travel through gaps between the vertebrae (which are held apart by intervertebral discs) and attach to the spinal cord by way of two roots: the dorsal and the ventral roots. The dorsal (posterior) nerve root contains fibers that carry sensory information into the spinal cord. Cell bodies of the dorsal neurons are clustered in a knot-like structure called a ganglion. A spinal nerve is a single nerve resulting from the fusion of the dorsal and ventral nerve roots. Fibers in the ventral (anterior) nerve roots exit from the ventral horn to carry motor information out of the spinal cord. Meninges of the Spinal Cord In addition to the bony protection offered by the vertebrae, the spinal cord is further protected by three layers of fibrous connective tissue, called the meninges. This transparent membrane clings to the outer surface of the brain and spinal cord. The arachnoid mater-a delicate layer resembling a cobweb-lies between the dura mater and the pia mater. All the nerve fibers of a single tract have a similar origination, destination, and function. As an example, the fibers of the spinothalamic tract originate in the spinal cord (spino-) and end in the thalamus (thalamic). In addition, they all convey sensations of pain, touch, and temperature to the thalamus in the brain. Note: All tracts exist on both sides of the spinal cord, but, in this illustration, the ascending tracts are highlighted on the left and the descending tracts on the right. Descending tracts conduct motor impulses down the spinal cord to skeletal muscles. The corticospinal tracts (also called the pyramidal tracts) are responsible for fine movements of hands, fingers, feet, and toes on the opposite side of the body. The extrapyramidal tracts are a group of tracts associated with balance and muscle tone. The spinothalamic tract relays sensations of temperature, pressure, pain, and touch. For example, sensory signals from the right side of the body are sent to the left side of the brain. Also, motor signals being sent to the right side of the body originate on the left side of the brain. This is why someone who suffers a stroke affecting motor centers in the left side of the brain will have weakness or paralysis on the right side of the body and vice versa. That Makes Sense To remember the difference between ascending and descending tracts, think about this: When you step on a nail, the sensation of pain ascends to your brain. Sensory nerves transmit impulses toward the spinal cord; once there, they travel up the spinal cord (ascend) along the ascending tract. As a further hint, remember that afferent (sensory) nerves link to the ascending tract. Motor nerves carry messages about movement; therefore, those impulses leave (or exit) the spinal cord along efferent (motor) nerves. Infection may be caused by several different bacteria or viruses that gain entry to the central nervous system by spreading from other locations in the body, such as from an ear or sinus infection. Bacterial meningitis occurs less often than viral meningitis, but it can be life threatening without immediate treatment. Symptoms of meningitis include fever, stiff neck, irritability, headache, drowsiness, and seizures. Infants with meningitis may have different symptoms, including poor feeding, bulging fontanelles, and a high-pitched cry. Viral meningitis usually causes milder symptoms, such as those similar to a cold or the flu. In fact, viral meningitis often goes undiagnosed because the symptoms are so mild. To diagnose meningitis, a sample of cerebrospinal fluid is obtained through a lumbar puncture. The fluid is then examined for bacteria and white blood cells, a sign of inflammation. Viral meningitis usually resolves on its own in 7 to 10 days, whereas bacterial meningitis requires hospitalization and treatment with intravenous antibiotics. Spinal Nerves Spinal nerves (part of the peripheral nervous system) relay information from the spinal cord to the rest of the body. The number of nerve fibers contained in a single nerve varies from a few to as many as a million. Myelin sheath Axons Blood vessels Most nerves contain both sensory and motor fibers and are called mixed nerves. A few nerves (such as the optic nerves) are sensory nerves and contain only sensory (afferent) fibers. Others are motor nerves and contain only motor (efferent) fibers and carry messages to muscles and glands. The four major plexuses are the cervical plexus, the brachial plexus, the lumbar plexus, and the sacral plexus. Phrenic nerve Axillary nerve Radial nerve Median nerve Ulnar nerve C1 C2 C3 C4 C5 C6 C7 C8 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 L1 L2 L3 the cervical plexus contains nerves that supply the muscles and skin of the neck, tops of the shoulders, and part of the head. Key nerves traveling into the arm from this region include the axillary nerve (which passes close to the armpit, making it susceptible to damage from the use of crutches), the radial nerve, the ulnar nerve, and the median nerve. The lumbar plexus-derived from the fibers of the first four lumbar vertebrae-supplies the thigh and leg. Irritation of this nerve causes severe pain down the back of the leg, a condition called sciatica. Femoral nerve L4 L5 S1 S2 S3 S4 S5 Co1 Sciatic nerve Dermatomes Each spinal nerve (except for C1) innervates a specific area of the skin. Clinicians assess sensation in the various dermatomes-using pinpricks and light touch-to identify the location of a nerve abnormality. Dermatomes are also used to assess and diagnose the level of a spinal cord injury. Following are two views of the dermatomes: the traditional upright position and, to more clearly show the distribution of dermatomes, a figure in a quadruped position. Males between the ages of 16 and 30 have the greatest risk, mainly because of their tendency for high-risk behaviors, although the incidence of spinal cord injuries among elderly populations is rising. Vehicle crashes are the leading cause of injury, followed by falls, acts of violence (mainly gunshot wounds), and sporting accidents. Injuries typically occur when a sudden, traumatic blow to the spine fractures or dislocates vertebrae. Displaced bone fragments, along with compression of the vertebrae, crush and destroy nerve fibers in the spinal cord. For example, if all sensory and motor function is lost below the site of injury, the injury is called complete. If some sensory or motor function remains below the site of injury, the injury is called incomplete. A loss of sensory and motor function in all or part of the trunk, legs, and pelvic organs-known as paraplegia-results from an injury between the levels of T1 and L1. An injury above the C5 vertebra produces a loss of sensory and motor function in the arms as well as the legs, trunk, and pelvic organs. An injury above C4 is especially serious because this is where the phrenic nerve exits the spinal cord. Because the phrenic nerve innervates the diaphragm, an injury here can cause respiratory failure. People with spinal cord injuries tend to suffer from a variety of medical complications, including chronic pain, bladder and bowel dysfunction, and an increased susceptibility to respiratory and heart problems. The average life expectancy for individuals with spinal cord injuries is significantly lower than life expectancies of those without spinal cord injuries. C4 Complete paralysis below the neck C6 Paralysis of hands, arms, trunk, and legs. T5 Paralysis of trunk and legs L5 Loss of function in legs and hips 196 Somatic Reflexes Reflexes are a quick, involuntary, predictable response to a stimulus. Reflexes employ a neural circuit called a reflex arc, which bypasses regions of the brain where conscious decisions are made. Some reflexes-called autonomic (visceral) reflexes-involve secretion from glands or the contraction of smooth muscle (such as dilation of the pupil). These reflexes are governed by autonomic neurons, which will be discussed later in this chapter. Somatic reflexes involve the contraction of a skeletal muscle after being stimulated by a somatic motor neuron. Somatic reflexes often help protect the body against harm-such as causing you to withdraw your hand from a hot stove. Specifically, skeletal muscles contain sensory receptors that send messages to the brain about the amount of stretch in a muscle as well as the movement of body parts. This allows the brain to emit signals to correct muscle tone and control movement; it also allows it to trigger a reflex to correct posture. For example, keeping your balance can be attributed to the reflexive contracting and relaxing of various muscles-all without your awareness. Life lesson: Babinski sign Used to evaluate disorders of the central nervous system, the plantar reflex occurs when the sole of the foot is stroked in a curved line from the heel to the toes with a blunt instrument. If the primary motor cortex or corticospinal tract is damaged, the stroking maneuver will elicit what is known as Babinski sign: the great toe will dorsiflex as smaller toes fan outward. Indeed, the brain performs numerous amazing functions, many of which remain beyond our grasp. Although smaller than the cerebrum, it contains more neurons than the rest of the brain combined. A thick bundle of nerves called the corpus callosum runs along the bottom of the fissure and serves to connect the two hemispheres. Gray and White Matter Like the spinal cord, the brain contains both gray and white matter. Unlike the spinal cord (in which gray matter forms the interior), in the brain, gray matter forms the surface. Specifically, gray matter (consisting of cell bodies and interneurons) covers the cerebrum and cerebellum in a layer called the cortex. Underneath the cortex is white matter, although gray matter exists in patches called nuclei throughout the white matter. The white matter contains bundles of axons that connect one part of the brain to another. In some locations, the dura mater separates to create spaces called dural sinuses. These sinuses collect blood that has passed through the brain and is on its way back to the heart. Arachnoid villus Brain: Gray matter White matter In some places, the dura mater extends inward and separates major portions of the brain.

The theory is that the less efficient method of washing dishes may increase microbial exposure acne on scalp purchase betnovate 20gm on line, and acne vacuum generic betnovate 20 gm on line, in turn acne under eyes best betnovate 20gm, boost microbiome development skin care with hyaluronic acid generic 20 gm betnovate amex. Microbiome disruption during this period can profoundly affect both health and development acne kits cheap 20 gm betnovate free shipping. Normally abundant species become rare acne los angeles discount betnovate 20 gm with mastercard, while once-rare species begin to proliferate. For example, one study discovered a sizable population of a bacterium called Lactobacillus johnsonii. This bacterium normally resides in the gut, where it produces enzymes that digest milk. Its appearance in the vagina seemed unusual until researchers considered that the neonate would be coated with, and ingest, the bacteria during the birth process. The sugar nourishes beneficial gut bacteria, helping good bacteria proliferate, which, in turn, inhibits the growth of harmful bacterial species. Life lesson: A bacterial link to obesity the incidence of obesity has become epidemic in the United States, particularly among children. Obesity results from an imbalance between food intake, basal metabolism, energy expenditure, and-it now appears-gut microbiota. Research has shown that obese humans and mice have a different mix of intestinal microbes compared with lean individuals. Specifically, the microbiota of an obese individual has an increased capacity to harvest energy from the diet, causing the individual to glean more calories from the same amount of food, thus gaining weight. In fact, simply colonizing lean mice with the microbiota from obese mice was enough to trigger a significant increase in total body fat in the lean mice. Not only are obese children more likely to be obese in adulthood, they are also more likely to develop various health disorders and, even worse, die prematurely. Children who take three or more courses of antibiotics before age 2 have an increased risk of early childhood obesity. When given early in life, antibiotics disrupt the intestinal microbiota, often eradicating bacteria needed to metabolize calories efficiently. The link between antibiotic ingestion and weight gain has been well-known in the ranching community for years. In fact, approximately three-fourths of all antibiotics in the United States are given to livestock, not to treat illness but to promote rapid growth and weight gain. However, it is becoming evident that antibiotics also disrupt the microbiome in ways still not completely understood. Low-diversity microbiomes have been linked to such disorders as diabetes, obesity, arthritis, inflammatory bowel disease, psychiatric disorders, and cancer. A key aspect of fostering overall health involves nurturing a robust microbiome throughout the lifespan. The microbiome evolves over time: building during the early years and declining with advanced age. First year of life Breastfeeding exposes infants to more than 700 species of bacteria and is crucial for establishing long-term health. At the end of the first year, the child has an individually distinct microbial profile. The intestinal microbiome resembles that of an adult in terms of composition and diversity. In healthy adults, the microbiome is resilient and can return to baseline levels over time. Age 65 years Advanced age triggers a broad shift in gut microbe populations; also, the number of microbial species decreases. Microbiome disruption during this period can profoundly affect both neurodevelopment and lifelong health. Such measures include the following: Consumption of a high-fiber, plant-based diet. Bacterial fermentation of a diet rich in fiber produces compounds that benefit the gut microbiota. Polyphenols are plant compounds that are particularly rich in such foods as blackberries, green tea, black tea, dark chocolate, olive oil, and red wine. The breakdown of these foods by the body produces substances that stimulate growth of healthy bacteria. Ingestion of beneficial live bacteria (probiotics) helps seed the gut with healthy microbes. Prebiotic-rich foods-such as artichokes, leeks, onions, garlic, jicama, bananas, asparagus, and apples-contain indigestible fibers that nourish and feed healthy bacteria in the gut. Regular consumption of fermented foods boosts the population of healthy bacteria while crowding out disease-causing species. Moderate exercise boosts the population of beneficial bacteria in the gut by as much as 40%. Spending time outside, especially having contact with plants and soil, provides exposure to microorganisms that add to microbiome diversity. Because antibiotics kill many good bacteria along with the bad, it is best to limit their use to situations in which they are clearly necessary. Threats to the Microbiome Antibiotic use may be the most significant culprit in microbiome disruption. Even so, experts have found that various lifestyle factors can also dramatically alter microbiome composition. These bacteria then trigger an immune response that depletes the microbiome of beneficial bacteria. Bacteria Bacteria-the chief inhabitants of the microbiome-are single-celled microscopic organisms. They come in a variety of shapes and sizes and are found practically everywhere on earth. Some species of bacteria have a capsule: a gelatinous covering that keeps the bacterium from drying out. For this reason, bacteria that have a capsule are more likely to cause disease compared with those without a capsule. A rigid cell wall composed of a polysaccharide molecule called peptidoglycan encloses the bacterium and gives the cell its shape. The composition of the cell wall varies widely between species, making it an important distinguishing factor between bacterial types. For example, genes that resist an antibiotic can spread rapidly through a bacterial population. The cytoplasmic membrane, composed of phospholipids and proteins, regulates the flow of materials into and out of the cell. These outgrowths allow bacteria to attach to other cells and surfaces (such as your teeth). Diplococci Diplococci are cocci that exist in sets of two, whereas monococci live singly. Once treatment stops, there is no guarantee that the intestinal microbiome will return to normal. The infection, which usually afflicts hospitalized patients, is very difficult to treat, and patients are left to suffer from intense diarrhea and abdominal pain. Once delivered (by way of an enema or colonoscopy), the good bacteria multiplied rapidly, squeezing out the C. In fact, one recent study involving 77 patients had an initial success rate of 91%. Because alterations in the gut microbiome are associated with multiple disorders, researchers are investigating the use of fecal microbiota transplantation in such conditions as inflammatory bowel disease, obesity, metabolic syndrome, irritable bowel syndrome, nonalcoholic fatty liver disease, and even autism. Whether or not the bacteria retain the dye determines whether the bacteria will be classified as gram negative or gram positive. However, the focus on one pathogen as the cause of a particular disease is beginning to change. In healthy individuals, potential pathogens coexist peacefully within the microbiome and produce no ill effects. Research is ongoing as scientists seek to discover why, and under what conditions, some pathogens trigger illness. Findings are beginning to show that what matters is not a particular bacterium, but the function of the microbiome as a whole. Some viruses have an additional layer surrounding the capsid: a spikey lipid membrane called an envelope. Viral Shapes the capsid may assume one of three basic shapes: helical, polyhedral, or complex. It then uses the sheath like a syringe to inject its nucleic acid into the target cell. These frequent changes make it difficult to create effective vaccines to protect humans against infection. Even though bacteria outnumber fungi in the microbiome by a thousand times, scientists speculate that our bodies host millions of fungal species. Granted, when the immune system is compromised, such as by antibiotics or chemotherapy, some fungal species can rage out of control and cause illness. Candida fungus normally resides on the skin as well as in the mouth, intestines, and vagina. But, when the microbiome is disrupted, it can overgrow, resulting in vaginitis or oral thrush. Because some fungi reproduce through tiny spores in the air, it is possible to inhale the spores or for them to land on the skin. However, it is becoming clear that the microbiome and the mycobiome have a symbiotic relationship that is a key factor in maintaining health. Archaea Three domains make up life on Earth: bacteria, archaea, and complex life (which includes plants, animals, and fungi). They are famous for residing in extreme environments, including hot springs and Antarctic ice. They also, it turns out, reside in the human gut and oral cavity, where they contribute to the human microbiome. Archaea look much like bacteria; and yet, biochemically, they are as different from bacteria as night is from day. Indeed, one expert described archaea as being "as different from bacteria as an orange is from a blue whale. Functionally, however, archaea employ unique metabolic pathways and perform functions that scientists are just beginning to discern. Archaea are an extremely diverse group of microbes that have proved difficult to study. Also, because archaea are a relatively new discovery, locating them in the vast ecosystem of the human body is tricky. Even so, it is a given that these microscopic organisms contribute significantly to the pool of genes governing health and disease. The cell membrane of archaea consists of a type of lipid not found in any other organism. The semi-rigid cell wall, which lies outside the cell membrane, lacks peptidoglycans, a staple in bacterial cell walls. There are most likely other structural differences, given that archaea are sensitive to different antibiotic drugs than are bacteria. Other possible appendages include protein networks that cells use to anchor themselves in large groups. Every healthy adult carries a mix of microorganisms that is basically similar, except for a few minor variations. The components of the microbiome are basically the same from one part of the body to another. The components of the microbiome vary considerably between sites on the body and between individuals. The one consistent feature among all bacterial species is the composition of the cell wall. Bacterial genes have just as great an influence on human health as human genes do. Bacteria within the microbiome stay within their own community; therefore, their genes do not influence health. Viruses are not cells but, rather, are bundles of genetic material surrounded by a protein shell. Viruses are single-celled microscopic organisms that inhabit almost every environment on earth. Imbalances in the microbiome have been linked to which of the following disorders Which technology has been shown to be effective in treating Clostridium difficile infections Discuss the characteristics, functions, and locations of the various types of epithelial tissue. Name nine types of connective tissue, identify their locations and functions in the body, and describe the matrix and components of each. Describe the characteristics and locations in the body of three types of muscle tissue. Describe the characteristics and locations of mucous, cutaneous, and serous membranes. Although the human body contains trillions of cells, all of those cells can be categorized as belonging to one of four distinct groups of tissue.

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