STUDY NOTES - first midterm old material.docx

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Brock University
Physical Education and Kinesiology
Joanna Komorowski

Standard anatomical position: Body erect, feet slightly apart, palms forward, thumbs away from body. Remember that “right” and “left” refer to the patient or the cadaver, NOT THE OBSERVER. 2 Fundamental divisions of body: Axial part = head, body and trunk Appendicular part = appendages or limbs attached to axis There are also regional terms that is used to designate specific areas within axial and appendicular part of body Planes / Sections: There are 3 planes 1. Sagittal plane: vertical plane that divide body into left & right parts. NOT RIGHT AND LEFT HALVES: This is because some planes are parasagittal plane. Where the cut off is not exactly in the middle. In order to have equal halves, midsagittal or median plane. 2. Frontal plane (Coronal): vertical plane that divide body into anterior and posterior parts. 3. Transverse (Horizontal) plane: horizontal plane that divides body into superior and inferior parts. (Traverse section = cross-section) 1 more section: Oblique section – plane is cut at an angle. Definitions: Superior: above Inferior: below Anterior (ventral): in front Posterior (dorsal): behind Medial: towards middle Lateral: away from middle Intermediate: between medial and lateral Proximal: closer Distal: further Superficial: towards body surface Deep: away from body surface Body cavities: Dorsal (posterior): Cranial and vertebral cavity. Cranial cavity unclosed by skull and houses the brain. Vertebral cavity enclosed by the vertebrae and houses the spinal cord. Both cavities are very well-protected. (Very strong and bony) Ventral (anterior): Thoracic cavity (superior) and abdominopelvic cavity (inferior) Thoracic cavity contains 2 lateral pleural cavities (lungs) and central pericardial cavity (heart). Thoracic cavity is surrounded by ribs and muscles of chest – decent protection. Abdominopelvic cavity (two parts) Superior – abdominal (stomach, intestine, spleen, liver) – nothing covering them – no protection Inferior – pelvic (in bony pelvis, contain urinary bladder, some reproductive organs and rectum) Bony pelvis sort of protects – protection is basic Diaphragm separates the thoracic and abdominopelvic cavities, nothing separates the abdominal and pelvic cavity Skin + derivatives (sweat & oil glands, hair, nails) = integumentary system Structure of skin: 2 distinct regions: Epidermis (superficial part of skin) – epithelial layer (thick, keratinized stratified squamous epithelium) Dermis (deep part of skin) – Connective tissues There is also the hypodermis, known as superficial fascia because it is superficial to the tough connective tissue wrapping of skeletal muscles, it consists mostly of adipose tissue– not really skin, but shares the skins protective functions. Contains areolar CT+ blood vessels, adipose tissue (store fat) Act as shock absorber, insulator. It thickens when weight is gained. It anchors skin to underlying structures with ability to slide. Epidermis isn’t vascularized, dermis and hypodermis is. Epidermis gets nutrition from diffusion. 4 types of epidermal cells: Keratinocytes: majority of epidermal cells. Main function is to produce keratin – fibrous protein that helps give the epidermis its protective properties. The lifespan of keratinocyte is 25-45 days. Melanocytes: spider shaped, creates the pigment melanin. Found in the deepest layer of the epidermis. As melanin is made, it is accumulated in the membrane bound granules called melanosomes and brought to the numerous branching processes, they are then taken to the nearby keratinocytes, and they accumulate on the superficial side of keratinocyte nucleus, forming a shield protecting UV rays. *Tanning – tanning produce melanin at a faster rate, this is to protect the nucleus from UV rays. Melanin is a dark colour. Number of melanocytes is the same between people; the difference is half-life, production rate of melanin etc. Langerhans cells, also called epidermal dendritic cells: star shaped: They are macrophages: ingest foreign substances, activate immune system. Migrate to epidermis from bone marrow. Merkel cells, also called tactile cells: at epidermis/dermis boundary, have disc-like sensory nerve ending – like touch receptors. The layers of epidermis (from deep to superficial) Stratum Basle: attached to dermis, consists of single row of stem cells – youngest keratinocytes. It has high mitotic index. 10-25% of the cells are melanocytes; also some Merkel cells are present. Stratum Spinosum: several cell layers thick. Contain web of keratin filaments attached to desmosomes. Name reflects when the cell is dried and dead – looks like tiny spiked iron balls. Contain keratinocytes and melanin granules. Also contain Langerhans cells – most abundant in this layer. Stratum Granulosum: three to five cell layers. Keratinization of cells begins – these cells flatten, their nuclei/organelles begin to disintegrate, they accumulate two types of granules. The keratohyalin and lamellated granules. Keratohyaline granules help to form keratin in the upper layers. The lamellated granules contain water-resistant glycolipids that are a major factor in slowing water loss. Cells are now struggling to be viable. They are too far from the capillaries, and are cut off from the nutrients by the glycolipids. Stratum Lucidum: two or three rows of clear, flat, dead keratinocytes – translucent. The Keratohyaline granules are in parallel arrays. Only found in thick skin. No more nourishment from capillaries. Stratum Corneum: 20 – 30 cell layers thick. They account for ¾ of the epidermal thickness. They are thickest on palm of hand & soles. They are dead cells filled with keratin fibrils – they are strong, protective and waterproof. Thick skins refers to skin that contain all 5 layers, thin skins to skin that contain only 4 layers – no stratum lucidum. Most of our body are soft skin other than the palm, fingertips, and soles of feet. Dermis: Strong, flexible connective tissue, the cells are fibroblasts, macrophages, some mast cells and white blood cells. It is semifluid matrix, embedded with collagen, elastin & reticular fibers – binds entire body together. Dermis is richly supplied with nerve fibers, blood and lymphatic vessels. Also contain hair follicles, oil & sweat glands. The dermis contains two layers, the thin superficial papillary layer, and the deep thick reticular layer. The top 20% of dermis is papillary, and the bottom 80% is reticular. Papillary layer: Fine interlacing collagen and elastic fibers form a loosely woven mat interspersed with small blood vessels. The looseness of this CT allows phagocytes and other defensive cells to wander freely as they patrol the area for bacteria. The superior surface is thrown into peg like projections called dermal papillae that indent the overlying epidermis. On palms of the hands and soles of feet, these papillae lie atop larger mounds called dermal ridges. Collectively, these skin ridges are called friction ridges, increase friction and enhance gripping ability of fingers and feet. These create finger prints. Reticular layer: Dense irregular fibrous CT. Network of blood vessels that nourish this layer lies between this layer and hypodermis – they are called Cutaneous plexus. The bundles of collagen fibers are parallel to the skin. Separations or less dense regions between these bundles form cleavage or tension lines in the skin. These externally invisible lines tend to run longitudinally in the skin of the head and limbs and in circular patterns around the neck and trunk. *When an incision is made parallel to these lines, the skin gapes less and heals more readily than when the incision is made across the tension line. Collagen fibers of the dermis give skin strength and resiliency that prevent most jabs and scrapes from penetrating the dermis. Collagen also binds to water, helping keep skin hydrated. Elastic fibers provide the stretch-recoil properties of skin. In addition to the epidermal ridges and tension lines, a third type of skin marking is flexure lines. They are dermal folds hat occur at or near joints, where dermis is tightly secured to deeper structures. Since skin cannot slide easily to accommodate joint movement, the dermis folds and deep skin creases form. Extreme stretching of stretching such as pregnancy can tear the dermis. This tearing is indicated by silvery white scars called striae. They are commonly called “stretch marks”. Short-term but acute trauma (such as burn, or wielding a hoe) can cause a blister, the separation of the epidermal and dermal layers by fluid-filled pocket. The pigments that contribute to skin colour: Melanin: Only pigment made in the skin, its two forms range in color from yellow to tan to reddish brown to black. Skin colour dependent on type, relative amount and keratinocyte retention of the pigment (how long keratinocyte can hold them). Carotene: yellow to orange pigment found in plant products (carrot). It accumulates in keratinocytes (mostly stratum corneum) and in fatty the fatty tissue of the hypodermis. Carotene can be converted to vitamin A, which is essential for normal vision, as well as for epidermal health. Hemoglobin: red blood cells circulating through the dermal capillaries, give the pinkish hue to skin. Cyanosis – decreased oxygen level in hemoglobin, give skin bluish colour. Caucasians have little melanin, the epidermis is nearly transparent, this allow for the hemoglobin colour to really show. Hair & Hair follicles Sense insects, guard head (physical trauma, heat loss, sun), shield eyes, and filter particles from inhaled air. Hard keratin (more durable, doesn’t flake) Hair shaft – Keratization is complete. Hair root – Keratization ongoing Hair shaft – the shape determines if the hair is straight or curly. If the shaft is flat, the hair/ribbon like in cross section, the hair is kinky If the shaft is oval, the hair is silky and wavy If the shaft is round, the hair is straight and course. The shaft has three layers Medulla - consists of large cells and air spaces. Medulla is the only part of the hair that contains soft keratin. Absent in fine hairs Cortex – bulky layer surrounding medulla, consists of several layers of flattened keratinocytes, melanin pigment is here Cuticle – single layer of overlapping cells (like singles on a roof). It helps to keep neighboring hairs apart. Most heavily keratinized part of the hair, provides strength and helps keep inner layers compacted. Split ends occur when the cuticles wear away at the tip of the hair shaft due to abrasion, the keratin fibrils in the cortex and medulla frizz out. Hair turn gray or white is result of rate of melanin pigment production is slowing down, and from the replacement of melanin by air bubbles in the hair shaft. Hair structures: Shaft: Part that projects from skin Root: part embedded in skin (in hair follicle) Bulb: deep end of follicle, expanded. Has papilla (contains knot of capillaries that supplies nutrients, and signals to grow) & root hair plexus (wraps around each bulb, bending the hair stimulates these endings, contribute to the ability of touch receptors) Follicle wall: contains outer CT root sheath, derived from dermis. Contains inner CT root sheath, derived mainly from an invagination of the epidermis. The sheath thins as they reach to the hair bulb. Hair matrix: fraction of a millimeter above bulb, dividing area of the hair bulb that produces the hair. Arrector pili muscle: bundle of smooth muscles associated with each hair follicle. Most hair follicles approach the skin surface at a slight angle. Arrector pili muscle is attached so that its contraction pulls the hair follicle into an upright position. It dimples skin- cause Goosebumps. Sebaceous glands: Holocrine (burst) gland that secretes sebum (oily – lubrication & waterproofing; bactericidal) Whitehead – When sebum keeps producing oil and gets clogged up in follicle Blackhead – When the oil in whitehead oxidizes and turns black Acne – Inflammation of the sebaceous glands, usually caused by bacterial infection. Clinical notes on hair: Vellus hair – Body of children and adult females – fine hair Terminal hair – coarser, longer hair of the eyebrows and scalp. Can be darker. At puberty terminal hair appear in the axillary and public region of both sexes and on the face and chest of males. Hair growth is affected by hormones such as androgen (male sex hormone, terminal hair). Hair growth is also affected by nutrition. Conditions that increase local dermal flow may enhance local hair growth (brick layers who carried their hod on one shoulder all the time developed one hairy shoulder) Hirsuitism – when adrenal gland or ovarian tumor secretes abnormally large amount of androgens. Excessive hair in women. Average rate of hair growth is 2.5mm per week – children grow faster Each follicle goes through growth cycles. In each cycle there is active phase ranging from weeks to years, then there is resting phase – during this phase the hair matrix cells die and the follicle base and bulb shrivel. After the resting phase, the matrix proliferates again and form new hair to replace the old one that has fallen out or will be pushed out by new hair. Head hair has longer active phase (can grow longer without falling out) eyebrow hair has shorter active phase (hair can’t grow very long) Alopecia is a natural process. A hair follicle only has a limited number of cycles, hair are not replaced as fast – begin balding. Male pattern baldness – genetically determined, sex influenced condition. Growth cycle becomes so short that many hairs never emerge from their follicles. This gene “switches on” in adulthood, this cause the testosterone to turn into DHT. No hormones to help hair growth. Nails: Also hard keratin like hair, it is a scale-like modification of epidermis - protective and useful tool Each nail contain free edge, body (visible attached portion) and root (embedded in the skin) The deeper layers of the epidermis extend beneath the nail as the nail bed, the nail is like the superficial keratinized layer Nails appear pink because of rich bed of capillaries in the dermis, but the lunula contain more tissues/cells therefore you can’t see the capillaries and therefore they appear white. The proximal and lateral borders of the nails are overlapped by skin folds they are called nail folds. The proximal nail fold is called cuticle or eponychium The region beneath the free edge of the nail where dirt accumulate is called hyponychium The proximal portion of the nail bed is called matrix and this makes new nails. Sweat glands: they are also called sudoriferous glands They are distributed over skin surface except for the nipples & part of external genitalia. There is 2.5million/person. Two types of sweat glands merocrine and apocrine Merocrine: More common; in palms, soles and forehead. Each is a simple, coiled, tubular gland. The secretory part lies coiled in the dermis, and the duct extends to open in a funnel-shaped pore at the skin surface. They secrete sweat – hypotonic solution, 99% water, some salts, and some other solutes. Normally swear is acidic with pH between 4 and 6. Sweating is regulated by sympathetic division; its major role is to prevent overheating. Sweating first begin on the forehead and then spreads inferiorly over the remainder of the body. Emotionally induced sweating begins on the palms, soles and axillae (armpits) and then spreads to other body parts. Apocrine – 2000/person, in the axillary and the anogential area. They are larger than merocrine; tend to lie deeper in dermis and even the hypodermis, their ducts empty into hair follicles. Their secretion contains the same components as sweat, plus fatty substances and proteins. It is more viscous and sometimes milky or yellowish. The secretion is odorless, but when the organic molecules are decomposed by bacteria on skin, it develops odor – body odor. Begin functioning at puberty under the influence of androgens. Not for thermoregulation, are activated sympathetic nerve fibers during pain and stress. Activity is increased during sexual foreplay, enlarge and recede with the phases of woman’s menstrual cycle, they might be sexual scent glands. They are both merocrine glands because they release through exocytosis (exocrine), they use vesicles to empty into ducts. Modified apocrine glands: Cerminous: found in lining of external ear canal, their secretion mixes with sebum to form cerumen or earwax. Mammary: secretes milk Functions of the skin: 1. Protection: a) chemical (secretions, melanin) b) physical (waterproof, barrier to trauma/bacterial invasion) c) biological (Langerhans cells in epidermis, macrophage in dermis). Note* not impermeable to gases, fat soluble vitamins & steroids, plant oleoresins, organic solvents, salts of heavy metals, penetration enhancers for drug admiration. 2. Excretion: Some N-containing wastes (urea); NaCl & H2O via sweat 3. Body temperature: sweating (0.5-12 L/day), vasoconstriction 4. Cutaneous sensation: feel on skin, pressure on skin, hair follicle receptor on wind, free nerve ending sense pain, temperature 5. Metabolic: production of vitamin D 6. Blood reservoir: Muscles need blood, can take this blood to muscle. Skin can hold a lot of blood (5% of body entire volume), it doesn’t need as much blood supply as other body parts. Burns: can be from heat, electricity, radiation, and chemical (acid) First concern is dehydration, second concern is infection First degree – only epidermis Second degree – epidermis and upper dermis Third degree – epidermis and dermis The deeper you go, the more danger you are – you are damaging the cells that cause the repair. Potential for repair is take skin from other part of the body, and then put it on the damaged skin. Called skin crafting. Skin might reject this though Rule of nines: volume of blood lost can be estimated by computing the percent of body surface burned. Dividing body into 11 areas worth 9% each. 1% for the genitals. Bone: is a living dynamic tissue which responds to its environment. 1. Bone reacts to amount of force applied by increasing the density & amount of roughening on bone or decreasing density when fore is reduced or eliminated. Deposition (body > bone) vs. reabsorption (bone > body) 2. Bone stores calcium – resorbed & transferred to bloodstream when needed. Functions of bone: 1. Support: Supports body when standing, cradles organ 2. Protection: Protects brain, spinal cord, vital organs of thorax 3. Movement: Muscles attach to bones by tendons, use bones as levers to move the body 4. Mineral Storage: Calcium and phosphate 5. Blood Cell Formation: Hematopoiesis occurs in marrow cavities of certain bone 6. Triglyceride (fat) storage: Fat is stored in bone cavities and represents a source of stored energy for the body. Compare structure of bony tissues and cartilages: Cartilage: features between dense CT & bone – it’s tough, but flexible 1. Avascular, no nerve fibers. This is why cartilage take long time to repair – relies on diffusion 2. Ground substance contains of GAG (glucose amino glycan – hold a lot of water) chondroitin sulfate & hyaluronic acid – also chondronectin (adhesive protein) 3. Collagen fibers – give strength (can have some elastic fibers) 4. Up to 80% H2O, gives it cushioning properties, can spring back to its original shape Some terms relating to cartilage: Perichondrium – membranous wrapping around cartilages, act like a girdle to resist outward expansion when cartilage is compressed. Perichondrium contains the blood vessels from which the nutrients diffuse to cartilage. In damaged areas, perichondrium can form scar tissues because poorly vascularized cartilage repairs, badly. Ossification of cartilage with aging is gradually replacing cartilage with bone (old person’s ribcage is not flexible, result is not as easy to breathe) Chondroblasts – high MR, immature cartilage cells – actively form cartilage Chondrocytes- Low MR: mature cartilage cells – maintain cartilage Lacunae: localized clusters of chondrocytes in cartilage – in cluster because they get trapped by the cartilage around them (like wiping a floor) Types of Cartilage 1. Hyaline cartilage: most abundant, the only fiber found in their matrix is collagen fibers; firm support + pliability; appear glassy blue-white; chondrocytes only 1-10% of volume. Location: embryonic skeleton, ends of long bones (epiphyseal plates in growing children), costal cartilages of ribs, cartilages of nose, trachea, larynx Function: support & reinforces; resilient cushioning & resists compressive stress. 2. Elastic cartilage: like hyaline cartilage but more elastic fibers in it. Location: external ear, epiglottis – (in these places because they need the cartilages to be bendy (for food to go down)) Function: Maintains shape while giving lots of flexibility 3. Fibrocartilage: Rows of chondrocytes alternating rows with thick collagen fibers; structural intermediate between hyaline cartilage & dense regular CT Location: intervertebral disks, pubic symphysis, discs of knee joints Function: tensile strength with ability to absorb compressive shock Bone: calcium salts give hardness & strength for support/protection of softer tissues; cavities for fat storage & synthesis of blood cells. Two types: axial and appendicular Axial: Skull, vertebral column, ribcage – most involved in protecting, supporting, or carrying other body parts. Appendicular: upper/lower limbs, girdles (attach limbs to axial skeleton) – used for locomotion Osteoblast – growing bone Osteocyte – maintain bone Osteoclast – digesting bone to remove calcium from bone (multi nucleus) Classification of bones Bones vary in size and shape, unique shape of each bone fulfills a particular need. Bone is classified by their SHAPE not their SIZE. All bones have: Compact bone provides the external surface Spongy (trabecular) bone – honeycomb of trabeculae Types of bones: 1. Long bone – much longer than wide, has a shaft + 2 round ends, mostly compact bone with hollow centre (marrow cavity); spongy bone is found in the two ends. All limb bones except for the kneecap, wrist/ankle bones are long bones. 2. Short bone – cube-shaped, primarily spongy bone, with thin outer layer of compact bone. Wrist, ankle, sesamoid bones are short bones. 3. Flat bone – thin, flattened, sometimes curved. Skull bones, ribs, breastbone are flat bones 4. Irregular bone – Complicated shapes, primarily spongy bone + thin covering layer of compact bone. Leftover bones – vertebrae & hip bones are irregular bones. Long bone: 1. Diaphysis – Tubular shaft of long bone = long axis of the bone. Collar of compact bone surrounding marrow cavity (medullary cavity). In adults, medullary cavity contains fat (yellow marrow or yellow bone marrow cavity) in babies, medullary cavity contains red blood marrow instead – as they grow the red blood marrow gets concentrated to epiphyses. 2. Epiphyses – extremities of a long bone; expanded for articulation with other bones. Compact bones forms thin outer layer; inferior filled with spongy bone. Have a thin layer of hyaline (articular) cartilage for forming joints. 3. Epiphyseal line – line between diaphysis & each epiphysis – it’s the remnant of epiphyseal plate. Epiphyseal plate – a disc of hyaline cartilage that grows during childhood – lengthens bone. When epiphyseal plate becomes line, growth ends. Membranes cover outer & inner surfaces of long bones. Periosteum covers the outer surface, contains osteoblasts and osteoclasts. Endosteum covers the inner surface (lines marrow cavity), and covers each trabeculae; delicate layer of CT that also contains osteoblasts & osteoclasts Structure of other bone types: All 3 other types have similar structure With Compact bone on the outside, spongy bone on the inside Compact covered with Periosteum & spongy lined with Endosteum. They are not cylindrical so no shaft, marrow cavity or epiphyses. They do contain bone marrow between trabeculae. COMPACT BONE: Osteon (Haversian) system: The structural unit of compact bone. Osteon: elongated cylinder orientated parallel to the long axis of bone. A single osteon is a group of hollow tubes of bone matrix – like the rings of a tree. Each of the matrix tube is called lamellar bone. The collagen fiber have a 90*change of orientation with each layer. This pattern is designed to withstand tension stress; adjacent lamellae reinforce one another to resist twisting. In each core is central canal or Haversian canal, contain small blood vessels and nerve fibers that serve the needs of osteon cells. There are also perforating or Volkmann’s canal, perpendicular to long axis bone & Haversian canals that connect the blood and nerve supply of Periosteum to those in the central canals and medullary cavity. Osteocytes: mature bone cells; sit within the lacunae within bony matrix in areas where adjacent lamellae meet. Canaliculi: like small version of Volkmann’s canal, connect the lacunae with each other, also connected to Haversian canal. Interstitial Lamellae: fill the gaps between osteons or are leftovers of osteons that were partially destroyed by bone remodelling. Circumferential lamellae: sheets of bone located just deep to Periosteum; extend around entire circumference of shaft – resist twisting of long bone. Spongy bone: Contains trabeculae (align precisely along lines of stress and help the bone resist stress), few cells thick, contain irregularly arranged lamellae and osteocytes interconnected by Canaliculi. No osteons Nutrients diffuse through Canaliculi from the marrow spaces between the trabeculae to reach the osteocytes. Bone formation and remodeling: Osteogenesis or Ossification means making something to become bone. This includes formation of bony skeleton in embryos, growth of bones during childhood & adolescence & remodelling/repair of bones in adults. 1. Intramembranous Ossification: bone develops from fibrous CT membrane containing mesenchymal (stem) cells. Cranial bones of the skull and clavicles – flat bones. Begins at about 8 weeks of embryonic development. 2. Endochondral Ossification: more common, bone develops via the replacement of hyaline cartilage. All bones below the skull (other than clavicle). Begins in second month of embryonic development. More complex because it require the cartilage to break down first before building bone. *In short bones, only the primary ossification centre are formed; most irregular bones are formed using several distinct ossification centres. When ossification is complete, hyaline cartilage remains: 1. On the epiphyseal surfaces as the articular cartilage. 2. At the junctions of diaphysis and epiphyses where it forms epiphyseal plates – where long bones continue to grow. Mechanisms of bone growth: During infancy & youth, long bones lengthen entirely by interstitial growth of the epiphyseal plates, and the bone grows in thickness by appositional growth. Most bones stop growing during adolescence or early adulthood – some facial bones (jaw, nose) continues to grow throughout life. As the long bone lengthens, the shape of the ends must be altered (remodel). As the length increases, external surface of ends made slimmer while internal surface is thickened. In summary, bone is destroyed by osteoclasts and laid down by osteoblasts on both the inner and outer surfaces of growing long bone. Epiphyseal plate stays roughly the same size throughout childhood & adolescence. Epiphyseal plate then becomes thinner; the cells multiply more and more slowly. Longitudinal growth ends when bone of the epiphysis & diaphysis fuses = epiphyseal plate closure (18 in females, 21 in males). Some hormones cause the epiphyseal plate to close quicker. Growth in width: Growth in width = appositional growth. Layers of bone are laid on top of one another 1. Osteoblasts on periosteal side secrete bone matrix 2. Osteoclasts on the endosteal side remove bone matrix Osteoblast is quicker than osteoclast, more deposition occurring, bone get thicker slowly. Parathyroid hormone control: PTH produced by parathyroid glands, PTH is released when blood is losing calcium. Increased PTH level stimulate osteoclasts to absorb bone, releasing calcium to blood. Parathyroid glad is posterior to thyroid gland (4 glands). Calcitonin is produced by parafollicular cells (in thyroid) – is opposite of PTH. Osteoporosis When bone resorption outpaces bone formation – bone become porous Some areas of skeleton especially vulnerable: spine, neck of femur. Estrogen and testosterone promote bone health by restraining osteoclast activity and promoting deposition of new bone (less of these hormones in adults) Other factors include: insufficient exercise, poor diet in calcium & protein, abnormal vitamin D receptors, smoking (reduce estrogen levels) Skeleton: There are 206 bones in skeleton, making up 20% of body weight. Axial skeleton: segregated into 3 major regions: the skull, vertebral column, and thoracic cage. 80 bones Skull: most complex. Contain 2 set of bones: cranial + facial = 22 bones. Most skull bones are flat bones (other than mandible); they are united by sutures (“stiches” – immovable joints) Facial bone form anterior part of skull & cranial bone form the rest Skull has eye orbits & paranasal sinuses, houses organs of hearing, 85 openings for nerve, blood vessel, and spinal cord. Cranium: Can be divided into vault and base Vault: forms superior, lateral, & posterior aspects of the skull + forehead Base: inferior aspect of skull, internally the base is divided into 3 areas: anterior fossa (highest), middle fossa, posterior fossa (lowest). The brain sits snugly in the cranial fossas. Cranium surrounds & protects brain and organs of hearing, balance. Cranium: 8 bones: Paired parietal & temporal bones, unpaired frontal, occipital, sphenoid and ethmoid bones. The bones are curved, allow them to be self-bracing, can be strong and quite thin (like eggshell) Frontal bone: Dome shaped bone; also forms the roof of the orbits & anterior cranial fossa. It articulates posteriorly with the parietal bones via the coronal suture. Supraorbital margins: thickened superior margins of the orbits that lie under the eyebrows – for shading Supraorbital foramen – Each supraorbital margin is pierced by his, which allows the supraorbital artery and nerve to pass to the forehead Glabella: The smooth portion of the frontal bone between the orbits. The areas lateral to the glabella is riddled internally with sinuses, called frontal sinuses. Parietal bone: Paired, form the superior & lateral aspects of the skull. Form bulk of the cranial vault. The 4 largest sutures occur where the parietal bones articulate with other bones. Parietal – parietal = sagittal suture 2 Parietal – frontal = coronal suture 2 parietal – occipital = lambdoid suture Parietal – temporal = squamous suture Occipital bone: Single bone at base of skull; helps form posterior aspect of skull, also form walls of the posterior cranial fossa – supports the cerebellum. Attaches to 2 parietal & 2 temporal, also attached to sphenoid bone Foramen magnum –hole at the base of skull – for passage of brain stem – spinal cord. Occipital condyle – on each side of foramen magnum is the site or articulation with first cervical vertebra. This permits the nodding motion External occipital protuberance – it is superior to foramen magnum; knob projection at the back of skull – more prominent in males. Temporal bone: Paired, form inferior & lateral aspects of skull and parts of the cranial floor. Located below the 2 parietal bones – have 4 different areas of region. 1. Squamous region: flattened, touches the squamous suture Zygomatic process meets zygomatic bone (cheekbone) Mandibular fossa – small oval – on the inferior surface of the zygomatic process, receives the condyle of the mandible (lower jawbone). This forms a freely movable joint. 2. Tympanic region: surrounds the external acoustic meatus (external ear canal). Below the external acoustic meatus is the needle-like styloid process – an attachment site for many tongue and neck muscles. 3. Mastoid region: contain mastoid process, an anchoring site for some neck muscles. 4. Petrous region – internal aspect of temporal bone (can’t easily be seen) Contributes to cranial base & houses middle and inner ear cavities. Jugular foramen – junction of the occipital and temporal bone allows the passage of the internal jugular vein and 3 cranial nerves. Carotid canal – Anterior to the jugular foramen, transmits the internal carotid artery into cranial cavity, The arteries are close to internal ear cavities – explain why we can hear our rapid pulse as thundering sound when excited. Internal acoustic meatus – positioned superolateral (top and side) to the jugular foramen, transmits cranial nerves. Sphenoid bone: bat-shaped Complex bone, difficult to visualize; articulates with all other cranial bones. (Keystone bone of the cranial sksleton) Forms base of middle cranial fossa, contributes to base of anterior cranial fossa. Consists of a central body and 3 pairs of processes: greater wings, lesser wings, pterygoid processes Within the body of the sphenoid are the paired sphenoid sinuses. Greater wing: project laterally from the sphenoid body, forming parts of the middle cranial fossa, and the dorsal walls of the orbit. Lesser wing: horn-like, form part of the floor of the anterior cranial fossa, and part of the medial walls of the orbits. Pterygoid process – project inferiorly from the junction of the body and greater wings, they anchor the pterygoid muscles (for chewing) Optic foramen (canal) – for optic nerves to pass to the eyes Superior orbital fi
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