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ANA 209 Exam 1 Lecture Notes

by: Sharon Liang

ANA 209 Exam 1 Lecture Notes ANA 209

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Sharon Liang

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Lecture Notes for Exam 1 Content
Principles of Human Anatomy
Dr. April Hatcher
Study Guide
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This 29 page Study Guide was uploaded by Sharon Liang on Sunday February 7, 2016. The Study Guide belongs to ANA 209 at University of Kentucky taught by Dr. April Hatcher in Winter 2016. Since its upload, it has received 214 views. For similar materials see Principles of Human Anatomy in Anatomy at University of Kentucky.


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Date Created: 02/07/16
ANA 209 Exam 1 Study Guide Tissues I  Tissues: group of cells of similar structure that perform a common function  4 primary tissues: 1) Epithelial 2) Connective 3) Muscle 4) Nervous Cells  Varying types, shapes, and numbers  All have interrelations Intercellular Substances (Matrix)  Types of intercellular substances 1) Amorphous ground substance  Affinity for water (swells)  Varies in ‘form’ from a stiff gel to a thin solid  Provides support for cells suspended in it  Acts as a diffusion medium 2) Fibrous material  Collagen  Reticular  Elastic 3) Fluids  Tissue fluid helps diffusion of oxygen and nutrients/wastes  Arises from blood vessels specifically post-capillary venules Epithelial Characteristics  Covers surfaces, lines cavities, forms glands  Closely opposed cells at a free surface (no cellular or extracellular elements here), exhibits polarity and membrane specializations  Anchored to connective tissue by basement membrane (sheet-like layer of intercellular material, mainly functions in support) and to each other by tight junctions  The epithelium of mucous membranes overlies a thin layer of areolar CT, blood vessels, and nerves called the lamina propria  Replicate often  Avascular, tightly packed, with little intracellular material Functions of Epithelium  Secretion  Sensory reception  Absorption  Excretion  Barrier Epithelium Classifications  Cell number 1) Simple (1 layer) a. Simple squamous: single layer of flat scale-like cells  Cells fit tightly together  Easily damaged  Found where diffusion takes place  Alveoli, capillaries b. Simple cuboidal: single layer of cube shaped cells  Mainly functions in secretion and absorption  Kidney tubules, salivary glands, ducts of thyroid, pancreas, liver 2) Stratified (multiple layers) a. Stratified squamous  Cell division occurs in lower layers and pushes outward as outer layers are lost  Found in areas of heavy wear and tear: epidermis, mouth, anus, esophagus, vagina b. Transitional: appearance of cells changes with tension  Found lining urinary system, especially the bladder  When empty numerous layers can be seen, when full few layers are seen 3) Pseudostratified (1 layer which appears to be multiple because nuclei at different levels in the deeper half of epithelium) a. Pseudostratified ciliated columnar: appears to be several layers but is actually one in which the cell nuclei are at different levels  Found lining upper portions of respiratory tract and oviducts  Contains numerous goblet cells which secrete mucous that is moved along by cilia  Cell shape 1) Squamous  Scale-like  Width and depth greater than height  Shape analogous to a fried egg Functions: allows rapid transport of substances across membranes and secretes serous fluid 2) Cuboidal  Width, depth, and height approximately equal  Centrally placed nuclei  Can contain a brush border of microvilli Functions: absorption and secretion; production/movement of mucous 3) Columnar  Height exceeds width and depth  Nuclei vertically oriented  Often shows a brush border of microvilli  May contain goblet cells Functions: absorption; secretion of mucous and other products Epithelial glands  Epithelial cells invaginate from the surface to form 2 types of glands 1) Exocrine: secrete products into ducts Types of secretions:  Serous: watery with lots of enzymes  Mucous: rich in mucin, a viscous glycoprotein  Mixed: seromucous  Oily: sebum 2) Endocrine: secrete product directly into bloodstream (hormone)  Pituitary, adrenal, testes, ovaries, pancreas  Can be simple of compound  Glands are classified based on the complexity of the duct (simple/unbranched vs compound/branched) or on shape of secretory unit (tubular vs alveolar/acinar) 1) Simple coiled tubular (Ex: sweat gland) 2) Compound acinar (Ex: mammary gland) 3) Compound tubuloacinar (Ex: pancreas)  Release products in different ways 1) Merocrine: granules released from cell (pancreas) 2) Apocrine: part of cell is released with granules (mammary gland) 3) Holocrine: whole cell dies and is secreted (sebaceous gland of hair follicle) 4) Cytogenous: whole living cell is released (testis/ovary) Tissues II Membranes specializations in epithelial tissues 1) Apical membrane specializations a. Microvilli  Covered by glococalyx – “sugar-coat”  Function to increase surface area for absorption/secretion  Microfilaments in core are anchored to the meshwork of microfilaments at the cell surface = terminal web  In fluid transporting epithelia (ex: kidney tubules and small intestine) accumulations of cells with microvilli form a brush border b. Cilia  Hair-like, motile processes, evaginations of cell membrane  Longer than microvilli (0.2 – 1.0 µm) they’re up to 10 µm  Core of microtubules  Function to move things over cell surfaces by beating in a wave-like fashion (ex: in respiratory and reproductive tracts) 2) Communication a. Gap junctions  Channels function in cell to cell communication (electrical and chemical) 3) Lateral/basal membrane specializations a. Tight junctions (zonula occludens)  Found only in epithelium  Band-like zone around periphery near apical border  Functions to seal surface membranes together b. Desmosomes (zonula adherens)  Sites of strong adhesion  Can be spot-like = desmosome or macula adherens  Can be belt-like = zonula adherens c. Hemi-desmosomes  On basal aspect of cell to anchor it to basal lamina Examples of Connective Tissues 1) Fibrous 2) Fluid (blood) 3) Adipose 4) Supportive Cartilage Bone Characteristics of Connective Tissue  Cells are far apart and surrounded by a matrix: fibers and ground substance a. Ground substance: ranges from fluid (in blood) to solid (in bone)  Amorphous, gel-like, huge molecules with high affinity for water  Proteoglycans are main component  Secreted by fibroblasts b. Fibers 1) Collagen (most abundant)  Very high levels in bone and dentin  Thick threads which are flexible but not elastic, high tensile strength (resists pulling force)  Found binding structures together (tendons, fascia, ligaments)  Usually found in packed fiber bundles  Abundant collagen fibers = dense connective tissue  Few collagen fibers = loose connective tissue 2) Elastic (less strength than collagen but easily stretched)  Often branched and arranged in networks  Found in elastic ligaments and arteries, vocal chords 3) Reticular (made of collagen, very thin)  Mesh-like pattern of arrangement  Thin, flexible, distensible  Liver, lymphatic tissue c. Cells 1) Fibroblasts (most common cell type in connective tissue)  Mainly responsible for collagen production 2) Macrophages (phagocytes, attack and ingest foreign particles)  Function in defense and immunity 3) Mast cell (largest cell type) Secretes:  Heparin: prevents blood clotting  Histamine: increases leakiness of capillaries Functions  Support  Bone and cartilage provide skeletal support for other tissues  Protection  Bony protection for soft organs (ribs, lungs, and heart)  Storage  Adipose tissue stores fat for energy  Bone stores calcium and phosphate ions  CT proper stores extracellular water  Defense  Immune responses, inflammation, homeostasis  Transport  Medium for passage of nutrients and wastes  Healing  Scar formation and contraction Connective Tissue vs Epithelium CT proper Epithelium Highly vascular Avascular Variable cellularity Highly cellular Variable amount of extracellular material Almost no extracellular material Surface surrounded by tissue Free surface Cell lacks basement membrane subjacent to Basement membrane cell cell Cell membranes nonpolar Cell membranes polar Loose vs Dense Connective Tissues 1) Loose: increased cells, decreased fibers  Delicate thin membrane (mesentery)  Fills space between muscles  Examples include areolar tissue in abdomen and adipose tissues 2) Dense (fibrous): decreased cells, increased fibers  Densely packed collagenous fibers with few fibroblasts  Poor blood supply, therefore slow healing  Irregular - Fibrous capsules - Dermis of skin  Regular - Tendon - Ligament - Aponeuroses  elastic - vocal cords - trachea, bronchii - aorta Integumentary System Characteristics  the integument (skin) is the largest organ in the body  the integumentary system includes skin, hair, nails, and cutaneous glands (sweat glands)  2 or more kinds of tissue grouped together performing a specialized function  Covers body and merges with mucous membranes near margins of body orifices (mouth, anus, and nose)  Composed of 2 main layers (epidermis and dermis) Epidermis  Primarily composed of stratified squamous epithelium  5 layers 1) Basale: dividing inner cells 2) Spinosum 3) Granulosum: keratohyaline granules 4) Lucidum: not present in thin skin 5) Corneum: no nuclei in cells, no organelles, dead cells, lots of keratin  Major cell type = keratinocyte: migrate from basal cell layer to outer, while migrating  Melanocytes also found here, primarily located in basal cell layer - Make melanin brown, provide UV protection, made in response to light  Hair color depends on amount and type of melanin in cortex of hair  Stem cells are undifferentiated cells that divide and produce more keratinocytes Skin Color  Melanin - Granules in epidermis - Everyone has same number of melanocytes, skin color differences affected by how much melanin is produced - More granules, more brown color - Freckles and moles are accumulations of melanin - Natural sunblock: more melanin towards the equator (UV damage/production of folic acid)  Underlying blood showing through skin - Caucasians and bruising Dermis  Composed of connective tissue  Richly supplied with blood vessels, cutaneous glands, and nerve endings A. Papillary layer: loose CT - Dermal papillae: finger-like projections into epidermis; upward waves - Epidermal ridges: opposite of dermal papillae; downward waves B. Reticular layer: dense CT - Tough, leathery - 3D arrangement of collagen fibers - Collagen fibers form thicker bundles so there’s less room for ground substance Skin Depth 1) Thick skin: palms of hands and soles of feet  No hair, thick epidermis  100 cells thick on average 2) Thin skin: everywhere else, hairy  15-25 cells thick (corneum)  Has hair, sebaceous glands, and sweat glands Hypodermis  Aka subcutaneous tissue: loose CT under dermis, fat (adipose tissue) located here  Pads the body and attaches skin to underlying tissues  Contains a fatty and membranous component  Not part of the skin Burns  Partial thickness a. First degree: involves only the epidermis b. Second degree: involves epidermis and some of the dermis  Full thickness c. Third degree: epidermis and dermis completely destroyed Functions of the Integumentary System  Protection - Against physical, chemical, and biological injury, UV radiation - Enhanced by secretions of specialized glands, increased pigment or hair (from melanocytes) - Hypertrophy or thickening  Sensation - Has numerous nerve endings that respond to heat, cold, touch, texture, pressure, vibration, and tissue injury  Water retention - A barrier to water - Prevents body from absorbing excess of losing excess water  Thermoregulation - Thermoreceptors monitor the temperature of the body surface - If cold, constriction of blood vessels in dermis - If warm, dilation of the dermal blood vessels, lose heat through the skin (sweat glands also assist by perspiring and cooling the skin via evaporation)  Vitamin D synthesis - Carries out initial steps in Vitamin D synthesis - Vitamin D important for bone development  Non-verbal communication - Important in communicating facial expressions as muscles of facial expression insert on the dermis - This allows for intricate facial expressions Accessory organs of the skin  Hair: keratinized (keratin = fibrous, waterproof protein) filaments that develop from invagination of epidermis called hair follicle which can be divided into bulb, root, and shaft - Erector pili muscle: attached to CT sheath of hair, contracts when cold to reduce surface area of skin - Has 3 layers: medulla, cortex, and cuticle Layers surrounding hair follicle: - Epithelial root sheath: outermost part, down growth of epidermal cells - Deepest part forms bulb which is invaginated by CT - ~2/3 from the bulb an outgrowth forms a sebaceous gland - CT root sheath: derived from the dermis  Cutaneous glands a. Sebaceous glands - Secrete an oily substance called sebum - Ducts open into hair follicle - Holocrine secretion: entire bag of oil (cell) is released into hair follicle - Keeps hair and skin soft and waterproof - Prevents excess evaporation from skin - Inhibits growth of bacteria - Under influence of sex hormones: excess production results in acne - Tarsal glands of eyelids are modified sebaceous glands and secretions ensure eyelids don’t stick together b. Sweat glands - Apocrine i. Sweat glands that function as “scent glands” ii. Found in the groin, axilla, areola, beards in men, nipple, genitalia, and anus iii. Most active during emotional stress iv. Empty into hair follicle v. Sex hormones lead to development of gland at puberty vi. High levels of proteins (steroids), mix with bacteria on skin surface and cause body odor vii. Responsible for pheromones in animals (maternal, territorial, courtship) - Merocrine (eccrine) i. Sweat glands that function in evaporative cooling ii. Function to carry heat away from body iii. Most abundant in palms, soles, back, and forehead iv. Mammary glands are modified sweat glands v. Not associated with hair follicles vi. Much more numerous than apocrine vii. Secrete in response to increased body temperature. Secretions contain water, NaCl, urea, ammonia viii. Function in temperature regulation  Nails - Derivatives of the stratum corneum - Modified epidermal derivatives in the form of protective keratinized plates - Nail plates rest on the nail bed and can be subdivided into: free edge, nail body, and nail root - At the proximal end of the nail, the nail bed thickens to form the nail matrix. The thickness of the nail matrix conceals the underlying dermal blood vessels so the proximal part of the nail appears as a white crescent, or lunule - Growth occurs at the nail matrix, located beneath the root of the nail. Growth proceeds toward the root of the lunule. - The hyponychium is the top layer of the nail bed underneath the nail plate - The eponychium is a zone of dead (aka cuticle) along the proximal border of the margin of the nail fold - The appearance of nails can be used in medical diagnosis. For example, swollen fingertips can indicate underlying heart of lung problems. Cartilage Characteristics  Specialized CT for rigidity and enduring stress in weight bearing  Arises from embryonic mesenchyme  A component of the skeletal system of the body along with bone  Abundant matrix with fibers embedded in a gel-like ground substance  Avascular, therefore healing is slow, via long-range diffusion Composition of cartilage 1) Cells A. Fibroblasts: outer layer cells that secrete collagen - Form dense CT capsule around developing cartilage = perichondrium B. Chondroblasts: cartilage forming cells - Differentiated from chondrogenic cells (found inside perichondrium) - Secrete ground substance of chondroitin sulphate around themselves - After they become trapped by their own secretions = chondrocytes - Deposit new matrix into intercellular space causing interstitial growth C. Chondrocytes: living cells capable of mitosis - Occupies space within ground substance called a lacuna - Continue to divide but are trapped in lacunae by their own secreted matrix, thus forming cell nests (isogenous groups) - This cell division causes the cartilage to grow by interstitial growth 2) Ground substance (intercellular substance, matrix)  Interstitial substance of all cartilage but proportions vary depending on type  Typically appears amorphous  Composed of mucopolysaccharides and chondroitin sulphate 3) Fibers: form meshwork embedded in ground substance  Amounts/proportions vary depending on cartilage type A. Type I/II collagen B. Elastic Cartilage growth 1) Appositional growth  Growth at the surface of the cartilage caused by the continued proliferation of chondrogenic cells into chondroblasts in the perichondrium  Causes the cartilage to enlarge as a result of layer by layer deposition of new cartilage 2) Interstitial growth  Growth from within (swelling, like bread rising)  In a new cartilage, chondroblasts continue mitosis, new chondroblasts are pushed away and continue to lay down their own matrix, therefore growth from within  In older cartilage, continued mitosis leads to cell nests because the matrix is less flexible preventing daughter cells from being pushed away Cartilage Types 1) Hyaline  Glassy/blue-white appearance  Found on ends of bones in synovial joints = articular cartilage  Found in nose, rings of trachea & bronchi, embryonic skeleton  3D arrangement of type II collagen fibers  Matrix is ground substance of hyaluronic acid, chondroitin sulfate, and keratin sulfate bound to proteoglycans (a protein) 2) Elastic  Contains numerous elastic fibers  Found in earlobes and larynx  Similar ground substance to hyaline  Does NOT calcify  Highly resilient 3) Fibrocartilage  Many collagenous fibers with few cells  Found in areas subject to great pressure: intervertebral disks, public symphysis  Large bundles of type I collagen  Chondrocytes in rows  Similar ground substance to others  Most strong of cartilage types Cauliflower Ear  Occurs when the external portion of the ear suffers a blow, and a blood clot of other fluid collects under the perichondrium. This separates the cartilage from the overlying perichondrium (its source of nutrients), leading to cartilage death. Bone Characteristics  Specialized for supporting weight  Dynamic  Major mineral storage area  Dense extracellular substance (calcium phosphate crystals and collagen fibers) Function  Support and protection - Shape - Weight support - Protects: brain, eyes, heart, reproductive organs  Movement - Muscle attach to bone and move the bones at the joints  Hematopoiesis (blood formation) - Hematopoiesis is first done by yolk sac then liver/spleen then finally the bone marrow as an adult - Red marrow: makes red blood cells, white blood cells, and platelets - Yellow marrow: fat  Storage - Reservoir of calcium and phosphate - Calcium levels are regulated by osteoclasts/osteoblasts Bone Composition 1) Cells A. Osteoblast - Immature cell type - Actively making osteoid (non-ossified, organic portion of bone) - Non-dividing cells, extensive rough endoplasmic reticulum = metabolically active - Found lining the surface of growing bone - Function to produce the organic matrix of bone, composed of: i. Type I collagen fibers ii. Synthesized in layers that alternate in direction for greater tensile strength iii. Ground substance iv. Primarily chondroitin sulfate B. Osteocyte - Former osteoblasts that have become trapped in the matrix they deposited - Non-dividing cells; located in cavities called lacunae - Have numerous interconnecting cytoplasmic processes occupying slender canals called canaliculi - Mature cell type, totally encased in bone matrix - Canaliculi are small canals within ossified matrix, containing slender cytoplasmic process - Interconnect osteocyte lacunae and ensure that all surfaces of the osteocyte are bathed by tissue fluid (nutrients and oxygen) - Osteocytes located within 200 µm radius of a blood capillary C. Osteoclast - Large, non-mitotic cells with multiple nuclei - Arise from circulating blood and bone marrow as monocytes or macrophages that are attracted to bare bone surface and then fuse with one another - Resorbs surplus or inferior bone matrix, as found in resorbing surfaces in depressions called Howship’s lacunae - Ruffled border of branching finger-like processes poking into surface of bone, ruffles increase surface area of cell to bone - Essentially a secretory cell, secretory vesicles fuse with cell membrane in the bottom of clefts between ruffles - Hydrolytic enzymes liberated by exocytosis digest the amorphous organic component 2) Bone matrix - 1/3 organic (collagen fibers and protein-carbohydrate complexes), 2/3 inorganic (hydroxyapatite, a crystallized calcium salt) - Osteoid (bone-like) tissue is bone tissue with uncalcified organic matrix - Calcification requires deposition of insoluble calcium salts - Calcification occurs only if concentration of calcium and phosphate ions reaches level required for calcium phosphate deposition - Ossification is a process whereby bone tissue is formed including secretion and calcification of bone matrix - Periosteum is a highly vascularized/innervated fibrous CT covering of external surface of bone and is divided into 2 layers i. Outer layer  Fibroblasts, fibrocytes, collagen fibers and ground substance ii. Inner layer  Osteogenic cells (fibroblast-like) that give rise to osteoblasts  Osteogenic cells constitute the inner layer of periosteum as well as the endosteum (lining of medullar cavities), Haversian canals and other soft tissue spaces  Osteogenic cells give rise to osteoblasts when stimulated to proliferate in areas that are well- vascularized  Always a stock of undifferentiated osteogenic cells constituting a self-renewing population Types of Bone 1) Spongy (cancellous) - Contains spicules/trabeculae of bone - Numerous spaces within it, resembling a sponge - Spaces filled with bone marrow 2) Compact - Composes outer surface of every bone in body - Contains tightly-packed structural units called osteons (Haversian systems) Compaction  Process by which spongy bone is transformed to compact bone - spongy bone exists as random trabeculae (spicules), the space between the spicules containing marrow cells and blood vessels - osteogenic cells persist on the trabecular surfaces and transform into osteoblasts - osteoblasts deposit new osteoid material on the trabeculae in a layer-like fashion (appositional growth) - with each layer that’s deposited the space becomes narrower and the trabeculae wider  Spaces in spongy bone are eliminated to form compact bone - eventually the marrow spaces are obliterated = compact bone - some spongy bone persists in the central region (marrow cavity) of each bone, the compacted regions form the denser outer collars (bone collar)  Once compaction is complete, osteons are formed - Compaction results in the filling of the marrow spaces by the concentric deposition of osteoid in a lamellar fashion - This forms the basic structural unit of compact bone = the osteon (Haversian system) Haversian Canal Systems  Osteons are called Haversian Canal Systems - Each osteon has been built around a blood vessel of the old marrow space - Each osteon appears as a number of concentric rings (lamellae) of bone tissue that defines an inner space = Haversian canal that houses one of two blood vessels - The blood vessels nourish the osteocytes of the osteon via diffusion of nutrients and oxygen through the bone fluid that fills each canaliculi  Volkmann’s travel perpendicular to Haversian canals - Adjacent Haversian canals are linked by passageways = Volkmann’s canals - Volkmann’s canals are continuous with the periosteum and transmit blood from this layer into the compact bone - Volkmann’s canals aren’t surrounded by concentric lamellae  Not all matrix is organized into osteons - The inner and outer portions of dense bone are arranged into outer and inner circumferential lamellae - Between these layers compact bone consists of mainly of osteons (Haversian systems) - Irregular patches of bone are called interstitial lamellae, remains of old osteons that were remodeled Classification of Bones Flat bones  Thin plate-like structures with broad surfaces, rather than actually flat  Ribs, scapula, parietal bone Long bones  Have longitudinal axis and expanded ends  Femur, humerus Short bones  Roughly cuboidal in shape with approximately equal lengths and widths  Carpal bones of the wrist and tarsal bones of the foot Irregular bones  Irregular or varied shape  Normally connected to several other bones  Vertebrae, maxilla, mandible Bone Markings  Markings occur on bones wherever fibrous tissues like ligaments, tendons, fascia, or intermuscular septa attach  Markings appear around puberty and become increasingly pronounced with advanced age Openings  Foramen: an opening through which blood vessels, nerves or ligaments pass  Meatus: a tube-like passageway running within a bone  Paranasal sinus: an air-filled cavity within a bone connected to the nasal cavity  Fissure: a narrow cleft-like opening between adjacent bones through which blood vessels or nerves pass  Groove or sulcus: a furrow or depression that accommodates a soft structure such as a blood vessel, nerve, or tendon Depressions  Fossa: a depression in or on a bone  Fontanel: dense CT filled space between skull bones at birth Processes  Processes that form joints - Condyle: a large, rounded articular prominence - Head: a rounded, articular projection supported on the constricted portion (neck) of a bone - Facet: a smooth flat surface  Processes to which tendons, ligaments, and other CTs attach - Tubercle: a small, rounded process - Tuberosity: a large, rounded, usually roughened process - Epicondyle: a prominence above a condyle - Trochanter: a large, blunt projection found only on the femur - Crest: a prominent border or ridge on a bone - Line: a less prominent ridge than a crest - Spinous process (spine): a sharp, slender process Bone Formation Methods of Bone Formation  Intramembranous ossification: bone forms directly from embryonic membranes - Process used to form non-weight-bearing bones (Ex: flat bones of the skull)  Endochondral bone formation: bone forms indirectly from cartilaginous templates - Most bones in the body are formed by endochondral ossification such as long bones - Bone forms from templates of hyaline cartilage = cartilage model Intramembranous Ossification Steps 1) Embryonic mesenchymal cells condense into a connective tissue sheet or “membrane” with increased vascularization 2) Osteoblasts differentiate from the mesenchymal cells  Osteoid secretion forms spicules of pre-bone  Osteocytes become attached by cytoplasmic processes 3) Calcium phosphate salts become incorporated (deposited into the osteoid matrix)  Osteoblasts become trapped within their own matrix and become osteocytes 4) Bone spicules continue to develop forming bony meshwork, spaces between are filled with bone marrow cells and blood vessels  Inner and outer aspects of the membranous bone plate undergo compaction to form an inner and outer table 5) Spongy bone core of the flat bone retains its trabecular appearance and remodeling is continual by osteoclasts and osteoblasts Endochondral Ossification Steps 1) Hyaline cartilage forms a tiny fetal template of future bone 2) The cartilaginous tissue is destroyed as the perichondrium calcifies  Bone collar forms on the cartilaginous template in the region of the diaphysis (shaft of bone) 3) Mineralization of hyaline cartilage template  Chondrocytes enlarge and become vacuolated  Lacunae enlarge as well, causing loss of matrix  Remaining cartilage between the lacunae becomes calcified through the deposition of calcium phosphate  Chondrocytes begin to die  Perichondrium becomes periosteum at periphery 4) Invasion of blood vessels  Chondrocytes die and osteogenic cells invade  A periosteal bud (piece of periosteum) invades the internal calcified cartilage, bringing with it osteogenic cells, blood vessels, and CT elements 5) Formation of the primary center of ossification  Internally, the marrow region is composed of spicules of calcified cartilage with a layer of new osteoid deposited over it  Osteoclasts begin resorbing both the calcified cartilage and the newly mineralized osteoid  Osteoblasts continue to form new bone  This primary (immature) bone lacks osteons  The true marrow cavity forms as the result of bone resorption by the osteoclasts 6) Formation of the secondary centers of ossification  These develop in the epiphysis (ends of long bone) postnatally  Similar to primary center but develops slower  Note: secondary ossification occurs in both ends, this illustration depicts the ossification center first, followed by formation of the marrow cavity  Ossification (growth) occurs in all directions forming an epiphyseal plate between the primary and secondary centers  Eventually this plate of cartilage erodes and the centers fuse, no further growth can occur following its destruction  The epiphyseal line on the bone surface, is the only remaining evidence of the plate Growth in Length and Width  Grow in length by endochondral ossification. The continued production of cartilage at the epiphyseal plate in the metaphysis causes elongation  Grow in width by appositional growth under the periosteum. The bone collar grows in thickness due to a layer-by-layer deposition of new bone. Bone Remodeling  Remodeling of bone: removal by osteoclasts (resorption) and redeposition by osteoblasts is required for the eventual formation of the size and shape of the adult bone - Repairs microfractures - Releases minerals into bloodstream - Reshapes bone in response to use or disuse Growth of Long Bones: Changes at the Metaphysis  Occurs in metaphysis region (lower end of epiphyseal plate) 1) Zone of quiescence (reserve cartilage) - Furthest from ossification center - Little growth 2) Zone of proliferation - Chondroblasts proliferate here causing active growth in length towards quiescent zone 3) Zone of maturation - Cell division stops - Cells and lacunae enlarge - Further growth in length 4) Zone of hypertrophy and calcification - Chondrocytes greatly enlarge - Matrix becomes calcified 5) Zone of degeneration - Chondrocytes degenerate - Matrix dissolves - Lacunae breakdown - Blood vessels invade with osteogenic cells 6) Zone of resorption - Osteoblasts surround calcified cartilage - Osteoid material is deposited on surface forming spongy bone trabeculae with calcified cartilage center - Osteoclasts resorb bone - Marrow cavity enlarges Termination of Bone Growth  Bone growth in length ceases when hormonal control of cartilage production at the epiphyseal plate stops  Once the epiphyseal plate stops producing new cartilage cells by continued proliferation, the mineralization front from the primary center of ossification moves up through the plate, completely calcifying it  Once this cartilaginous plate is calcified, it in turn is resorbed by osteoclasts  The erosion of both plate results in the fusion of the 3 centers of ossification into a confluent marrow cavity  Growth stops at this point Hormonal Control of Bone Deposition/Resorption 1) Gonadal (sex) hormones  Precocious sexual development causes accelerated skeletal maturation and results in short stature 2) Growth hormones  Anterior pituitary regulates growth of bone  Hypersecretion results in accelerated bone growth, hyposecretion causes shortness of stature Bone Repair after Fracture 1) Hematoma formation  Cells and blood vessels invade at fracture site, composed of clotted blood 2) Soft callus formation  Deposition of collagen and fibrocartilage 3) Hard callus formation  Osteoblasts deposit a temporary bony collar around fracture to unite bony fragments  Endochondral ossification follows 4) Bone remodeling  Osteoclasts clean bone fragments  Osteoblasts deposit spongy bone and convert to compact bone Axial Skeleton  Comprises the bones and cartilage of the head, neck, and trunk that form the axis of the body: skull, hyoid bone, vertebral column, and thoracic cage Bone Classification  All bones have an outer shell of compact bone and an intermedullary cavity region composed of spongy bone  The amount of compact bone is variable, giving individual bones their unique shape Bones of the Cranium  The skull is composed of a cranium (bones that enclose the brain) and a facial skeleton  8 bones forming the cranium: - 1: frontal bone, sphenoid bone, ethmoid bone, and occipital bone - 2: parietal bones, temporal bones (each paired separately)  The pterion, point where the 4 bones meet (parietal, frontal, temporal, and sphenoid), is the weakest point of the skull and is susceptible to fracture with head injury  The paired parietal bones meet at the midline sagittal suture  The coronal suture separates the frontal bone from the anterior aspect of the parietal bones  The lambdoidal suture separates the occipital bone from the posterior aspect of the parietal bones  Small bones trapped in the suture are sutural bones Floor of the Cranial Cavity  The bones of the floor of the skull form 3 step-like depressions (fossae) 1) Anterior cranial fossa: houses the frontal lobe of the brain 2) Middle cranial fossa: houses the temporal lobe of the brain 3) Posterior cranial fossa: houses the cerebellum Paranasal Sinuses  There are spaces of cavities within bones of the skeleton that lighten the weight of the skull. These spaces are considered extensions of the nasal cavity and therefore are lined by the same type of respiratory mucous membrane.  4 paranasal sinuses named for the bones in which they’re located - Frontal - Ethmoid - Maxillary - Sphenoid Bones of the Facial Skeleton  2: maxilla, zygomatic bones, palatine bones, lacrimal bones, nasal bones, inferior nasal conchae  1: mandible, vomer Hyoid Bone  Referred to as a “floating bone” as it doesn’t directly articulate with other bones but is held in place with muscles and membranes  The larynx is suspended from the hyoid, which is composed of: body, greater horn, and lesser horn Vertebral Column  Composed of vertebrae, intervertebral disks, sacrum, coccyx  Forms central axis of skeleton  4 curvatures: cervical, thoracic, lumbar, and sacral Parts of a Typical Vertebrae  Typical vertebrae have: - Weight bearing: body - Protection: lamina, pedicle - Movement: spinous process, transverse process - Obstruction of movement: articulating process  Each vertebra is separated from the other by an intervertebral disc. Each disc is composed of an outer fibrous annulus fibrosis and a central gel-like region, the nucleus pulposus  The lamina and pedicle together form the vertebral arch (bony roof) of the vertebral canal.  The underlying body of the vertebra forms the final component of the vertebral canal.  The vertebral canal is the bony tunnel along the length of the entire vertebral column that protects the spinal cord lying within it.  When viewed from the lateral aspect, there are 2 notches (superior/inferior intervertebral notch)  When 2 vertebrae are stacked on top of one another, the 2 notches come together to form the intervertebral foramen. This is the site of exit of spinal nerves as they arise from the spinal cord and pass out into the periphery of the body. The Thoracic Cage  Composed of a series of 12 ribs  Ribs articulate posteriorly with the vertebra, and when extending anteriorly either join the sternum via a costal cartilage, or join a common costal cartilage which then articulates the sternum, which is composed of 3 parts: manubrium, body, and xiphoid process. The sternum resembles a dagger, the handle is the manubrium, the blade is the body and the tip is the xiphoid process Typical Rib  “Typical ribs” are numbered 2-10. Rib 1 is an atypical shape, and ribs 11-12 are “floating”  Each rib has a head, neck, tubercle, and shaft  The head articulates with the body of the vertebrae, the tubercle articulates with the transverse process of the vertebra and the terminal part of the shaft, articulates with the sternum via a costal cartilage Appendicular Skeleton  Consists of 4 appendages (2 upper and 2 lower limbs). The appendages must be attached to the axial skeleton and this task is accomplished by a “girdle” Pectoral Girdle  Attaches the upper limb to the axial skeleton  Composed of 2 bones (clavicle (anteriorly) and scapula (posteriorly))  The clavicle extends between the sternum and the acromion of the scapula. It effectively pushes the scapula posteriorly away from the posterior thoracic wall. A broken clavicle allows the upper limb to fall forward  The spine of the scapula protrudes posteriorly, while the acromion protrudes anteriorly, from behind to articulate with the clavicle  The head of the humerus articulates with the glenoid fossa of the scapula Bones of the Upper Limb  The upper limb is composed of 3 main regions 1) Arm - There’s a single long bone in the arm (humerus) seen here in an anterior view. The head articulates with the glenoid fossa of the scapula. There are 2 large tubercles (greater and lesser) and an intervening intertubercular groove. - The tubercles exist because large muscles attach to these regions. Note the large deltoid tuberosity where the deltoid muscle attaches. The medial and lateral epicondyles are also common forearm muscle attachment sites - The distal end of the humerus is the site of the elbow joint. This joint has a more complex arrangement than the shoulder joint. The humerus has 2 separate articulating surfaces: capitulum (lateral) and trochlea (medial). - The capitulum articulates with the head of the radius while the trochlea articulates with the proximal head of the ulna. 2) Forearm - There are 2 long bones in the forearm: radius (lateral) and ulna (medial), which are both seen from the anterior view - There 2 bones are held together by a stout membrane-like fibrous join (interosseous membrane). - At the proximal aspect, you can see the trochlear notch where the trochlea articulates, as well as the head of the radius where the capitulum articulates. There’s one additional articulation (the radial notch), where the head of the radius rotates against the ulna - Note the prominent tuberosity on the proximal region of the radius. The biceps brachii attaches here for supination - Note the 2 styloid (pen-like) processes one on each bone at distal ends - Note that only the distal end of the radius articulates with the carpal bones of the wrist. The ulna isn’t involved in the wrist joint but once again the 2 bones articulate with each other at the ulnar notch on the radius 3) Hand  Wrist: has 8 carpal bones organized into 2 rows a. Proximal - Scaphoid - Lunate - Triquetrum - Pisiform b. Distal - Trapezium - Trapezoid - Capitate - Hamate  The remaining rows of bones are the metacarpals followed by the proximal, middle, and distal phalanges  The metacarpals form the palm of the hand while the phalanges form the fingers  Note that the thumb lacks a middle phalanx Pelvic Girdle  The adult pelvic girdle is composed of 3 bones (left and right hip bone) and the intervening sacrum, which is an axial skeleton component.  2 hip bones are held together anteriorly by a very stout pubic symphysis (fibrocartilage joint)  Posteriorly there’s a sacroiliac joint on each side of the sacrum  Each hip bone is formed embryologically from 3 bones: ilium, ischium, and pubis. The bones fuse in the central region of the acetabulum where the head of the femur inserts at the hip joint. Bones of the Lower Limb  The lower limbs are also made up of 3 regions 1) Thigh (from hip to knee) - Like the upper limb, there’s a single bone in the first region of the limb (femur). The head of the femur articulates with the acetabulum of the hip bone at the hip joint - There’s a greater and lesser trochanter on the proximal end and lateral and medial epicondyles at the distal end of the femur - The patella is the largest sesamoid bone in the body (being located in the patellar ligament). It has a posterior articular surface that participates in the knee joint. 2) Leg (from knee to ankle) - Like the upper limb, there are 2 bones in the 2 ndregion of the limb (tibia (medial) and fibula (lateral)). These bones are anchored by a sturdy fibrous joint (interosseous membrane) - Note that the femur only articulates with the tibia at the knee joint. There are proximal and distal tibiofibular joints between the 2 bones. - Each bone forms one side of the bonyprotuberance at the ankle (lateral and medial malleoli). 3) Foot (ankle to toes)  Tarsal bones of the ankle are arranged in 3 rows: proximal, middle, and distal. However, the shape and size of these bones is highly various  Proximal: talus, calcaneus  Middle: navicular, cuboid  Distal: medial cuneiform, intermediate cuneiform, and lateral cuneiform  Distal to the tarsal bones are a row of metatarsal bones. Distal to those are the phalanges: proximal, middle and distal  The big toe lacks a middle phalanx. Articulations  Synovial joints are diarthrotic  Located at the end of long bones  Permit a wide range of motions  Articulating surfaces are covered by hyaline cartilage


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