Study Guide for Exam 2 Anatomy and Physiology!
Study Guide for Exam 2 Anatomy and Physiology! BSC2085
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This 31 page Study Guide was uploaded by Hannah Hartman on Sunday October 16, 2016. The Study Guide belongs to BSC2085 at Florida State University taught by Dr. Yung Su in Fall 2016. Since its upload, it has received 24 views. For similar materials see Anatomy & Physiology 1 in biological science at Florida State University.
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Date Created: 10/16/16
Chapter 5: The Integumentary System An introduction to the integumentary system: The Integument Is the largest system of the body o 16% of body weight o 1.5 to 2 m2 in area o The integument is made up of two parts Cutaneous membrane (skin) Accessory structures Cutaneous Membrane: consist of two components: o Outer epidermis Superficial epithelium (epithelial tissues) o Inner dermis Connective tissues Accessory Structures o Originate in the dermis o Extend through the epidermis to skin surface. Includes: Hair Nails Multicellular exocrine glands The integumentary system is connected to: o Cardiovascular system: By blood vessels in the dermis o Nervous system: By sensory receptors that detect stimuli for pain, touch, and temperature Hypodermis (Superficial Fascia or Subcutaneous Layer) – not considered part of the integumentary system o Located below the dermis o Composed of loose connective tissue o Location of hypodermic injections Five main functions of skin: o Protection of underlying tissues and organs o Excretion of salts, water, and organic wastes (glands) o Maintenance of body temperature (insulation and evaporation) o Production of melanin, keratin, vitamin D3, and storage of lipids o Detection of touch, pressure, pain, and temperature The Epidermis o Is avascular stratified (multiple layers) squamous (flat) epithelium Nutrients and oxygen diffuse from capillaries in the dermis. o Dominated by keratinocytes (most abundant type of epithelial cells) – contain large amounts of the protein keratin (this is a helical protein fiber that gives the skin strength) o WE have epidermal ridges and dermal papilla that help lock the two together. They are also the basis for fingerprints. o Thin Skin Covers most of the body Has four layers of keratinocytes o Thick Skin o Covers the palms of the hands and soles of the feet o Has five layers of keratinocytes o Structures of the Epidermis The five strata of keratinocytes in thick skin From basal lamina to free surface (from inferior layer to superior layer) Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum (missing in thin skin) Stratum corneum Epidermal Layers: 1 Stratum Basale o Is attached to basement membrane by hemidesmosomes – the basement membrane is then attached to the connective tissue. o Forms a strong bond between epidermis and dermis o Forms epidermal ridges (basis of fingerprints) – this helps to incresae the surface area betewen the epidermis and the dermis It also provides a greater area of surface area for movement of nutrients. o Dermal papillae (tiny mounds) – projections from the dermis Increase the area of basement membrane Strengthen attachment between epidermis and dermis Has many basal cells, or germinative cells o Ridge patterns on skin increases surface area and friction, ensuring a secure grip. determined by genetics and uterine environment during fetal development. Identical twins do not have the same fingerprints. o Specialized Cells of Stratum Basale Merkel cells – specialized epithelial tactile cells Found in hairless skin (e.g. the palm) Respond to touch (trigger nervous system) Melanocytes Contain the pigment melanin – notice the difference between melanin (skin pigment) and melatonin (the neurotransmitter) This colors skin, hair, irises, etc. Scattered throughout stratum basale 2 Stratum Spinosum — the “spiny layer” o Produced by division of stratum basale o Eight to ten layers of keratinocytes bound by smosome s (remember desmosomes link cells to eachother!) o Cells shrink until cytoskeletons stick out (looks spiny) – under normal histological preparations o Continue to divide, increasing thickness of epithelium o Contain dendritic (Langerhans) cells, active in immune response – defend against microorganisms that get past superficial layers of epidermis and defend against superficial skin cancers. Langerhan cells presents microorganism fragments to various B or T cells, activating an immune response. 3 Stratum Granulosum — the “grainy layer” (here the cells begin to die off) o Stops dividing, starts producing: Keratin A tough, fibrous protein Makes up hair and nails Keratohyalin (”cellular cement” – causes keratin fibers to link to one another) Dense granules Crosslink keratin fibers Note: as keratin accumulates, the cell flatten and its plasma membrane thickens and becomes less permeable. The cell becomes dehydrated. o Cells of Stratum Granulosum Produce protein fibers Dehydrate and die (organelles disintegrate) Create tightly interlocked layer of keratin surrounded by keratohyalin Keratohyalin cross links keratin and dehydrates cells 4 Stratum Lucidum — the “clear layer” o Found only in thick skin (e.g. palms and the soles of the feet; only 1 cell layer thick) o Covers stratum granulosum o Cells here are flattened, densely packed with keratin and are devoid of organelles o This layer has some slight waterproofing ability. 5 Stratum Corneum — the “horn layer” (latin cornu = “horn”) o Exposed surface of skin (15 to 30 layers of keratinized cells) o Water resistant, not water proof! o Shed and replaced every two weeks o All exposed skin surfaces (except the anterior of the eyes) undergo cornification (keratinization) – formation of protective, superficial layers of cells filled with keratin This is a very strong layer where the cells are linked together by desmosomes. Keratinization o The formation of a layer of dead, protective cells filled with keratin o Occurs on all exposed skin surfaces except eyes o Skin life cycle It takes 7 to 10 days for a cell to move from stratum basale to stratum corneum Once there, cells may remain at stratum corneum for an additional 2 weeks before shedding off Perspiration o Insensible perspiration Interstitial fluid lost by evaporation through the stratum corneum Lose approx. 500mL or 1 pint of H2O per day Any water not lost through sweat glands is considered insensible perspiration o Sensible perspiration Water excreted by sweat glands o Dehydration results: From damage to stratum corneum (e.g., burns and blisters [insensible perspiration]) From immersion in hypertonic solution (e.g., seawater [osmosis]) – remember skin is not waterproof! Hydration o Results from immersion in hypotonic solution (e.g., freshwater [osmosis]) o Causes swelling of epithelial cells, evident on the palms and soles Note: why do wrinkles form on your fingers and toes when submerged in water? You are hypertonic to the water around you, so your body picks up more water. This is a neural response. Skin Color Skin Color Is Influenced by Two Pigments o Blood circulation (red blood cells) can also affect skin color – if you have blood rushing to an area it will turn red (flushed). o Carotene Orangeyellow pigment Found in orange vegetables Carrots, squashes – if overconsumption, can turn skin orangish *+(Carotenemia) Accumulates in epidermal cells and fatty tissues of the dermis Can be converted to vitamin A – used for maintenance of epithelia and photoreceptor function Lack of vitamin A causes night blindness (nyctalopia) o Melanin Yellowbrown or black pigment Produced by melanocytes in stratum basale Synthesis of melanin requires the amino acid tyrosine Stored in transport vesicles (melanosomes) Transferred to keratinocytes Note: albino individuals do have melanocytes. However, the melanocytes do not have the ability to produce melanin. Difference in skin pigmentation caused by amount of melanin synthesized, not by the number of melanocytes Function of Melanocytes o Melanin protects skin from sun damage o Ultraviolet (UV) radiation Causes DNA mutations and burns that lead to cancer and wrinkles Melanosomes of keratinocytes concentrate around the cell nucleus to protect DNA o Skin color depends on melanin production, not number of melanocytes o With UV light, melanin pigments absorb radiation and prevent damage to the DNA of melanocytes. Capillaries and Skin Color o Oxygenated red blood contributes to skin color Blood vessels dilate from heat, skin reddens Blood flow decreases, skin pales o Cyanosis Bluish skin tint Caused by severe reduction in blood flow or oxygenation Illness and Skin Color o Jaundice – caused by build up of bile produced by the liver Yellow color o Pituitary tumor – caused by excess MSH (melanocytestimulating hormone) production Extremely bronze tan o Addison’s disease – disease of pituitary gland – releases more ACTH (adrenocorticotropic hormone), similar effect on skin color as MSH Skin will look bronze in appearance, usually due to pitutiary tumor or adenal gland tumor. This causes secretion of more adrenocorticosteroids o Vitiligo Loss of color due to loss of melanocytes (appears as patches, possibly caused by autoimmune reaction against cells by antibodies) Melanocytes die off, causing ”spots” on the skin Vitamin D3 Epidermal cells produce cholecalciferol (vitamin D3) in the presence of UV radiation Liver and kidneys convert vitamin D3 into calcitriol Hormone that aids absorption of calcium and phosphorus from food in intestine Insufficient vitamin D3 Can cause rickets (bending of weakened bones under body weight) Caused by insufficient sunlight exposure or dietary intake of Vitamin D3 (added to milk by dairy companies) Vitamin D3 is a precursor of calcitriol – a hormones produced by kidneys that is needed to absorb calcium from the foods (bone growth and strength) Epidermal Growth Factor (EGF) Powerful peptide growth factor Produced by glands (salivary and duodenum) Used in laboratories to grow skin grafts Functions of EGF o Promotes division of germinative cells o Accelerates keratin production o Stimulates epidermal repair o Stimulates glandular secretion The Dermis Located between epidermis and subcutaneous layer Anchors epidermal accessory structures (hair follicles, sweat glands) Two components o Outer papillary layer – much smaller than the reticular layer o Deep reticular layer Fun fact: tattoos are not in the epidermis, but the dermis. This is why they stay much longer than temporary tattoos. 1 The Papillary Layer o Consists of areolar tissue o Contains smaller capillaries, lymphatics (vessels that drain fluid left over by capillaries), and sensory neurons o Has dermal papillae projecting between epidermal ridges 2 The Reticular Layer o Consists of dense irregular connective tissue o Contains larger blood vessels, lymphatic vessels, and nerve fibers o Contains collagen and elastic fibers – this provides flexibility and strength o Contains connective tissue proper Dermatitis o An inflammation of the papillary layer o Caused by infection, radiation, mechanical irritation, or chemicals (ex. poison ivy) o Characterized by itch or pain o Inflammation can rapidly spread across the entire integument Dermal Strength and Elasticity o Presence of two types of fibers Collagen fibers Very strong, resist stretching but bend easily Provide flexibility (easily bent or twisted) Elastic fibers Permit stretching and then recoil to original length Provides fexibility (however ,collagen fibers limit flexibility to prevent damage to tissue) Skin turgor – caused by H2O content of skin Provides flexibility and resilience Dehydrated skin shows loss of turgor (pinching skin causes dehydrated skin to stay pinched, hydrated skin will flatten out) Cleavage Lines – formed from o Collage n and elasti fibers in the dermis Arranged in parallel bundles Resist force in a specific direction connective tissue fibers o Cleavage (tension/Langer) lines establish important patterns A parallel cut remains shut, heals well A cut across (right angle) pulls open and scars Note: surgeons choose incisions parallel to the cleavage lines to reduce scarring Skin Damage Sagging and wrinkles (reduced skin elasticity) are caused by: o Dehydration o Age o Hormonal changes o UV exposure o Wrinkles can be treated with RetinA (vitamin A derivative ) to stimulate skin repair. Effectiveness varies between individuals. Stretch marks – (collagen fibers snap and break, so when the skin goes back to normal size, the skin cannot recoil back into its original form) thickened tissue resulting from excessive stretching of skin due to: o Pregnancy o Weight gain Epidermis must receive nutrition from the dermis. If a bone cuts off this connection, the dermal layers will die off and cannot replace epidermal tissue. Decubitus ulcers – bedsores caused by problems with dermal circulation o Caused by compression of superficial blood vessels o Sores most common on skin covering joints or bony prominences o Affects epidermis and dermis Kills epithelial cells (easier for bacteria to invade) Erodes dermal tissues Innervation of the Skin Nerve fibers in skin control: o Blood flow – based on both emotional responses (nervousness) and physical response (heat) o Gland secretions o Sensory receptors Light touch— tactile (Meissner’s) corpuscles , located in dermal papillae Deep pressure and vibration— lamellated (pacinian) corpuscles , in the reticular layer The Hypodermis (Subcutaneous Layer) Lies below the integument (under the dermis) Stabilizes the skin Allows separate movement Made of elastic areolar and adipose tissues (subcutaneous fat) – distribution determined by hormones, removed by liposuction (lipoplasty) Connected to the reticular layer of integument by connective tissue fibers Few capillaries and no vital organs The site of subcutaneous injections using hypodermic needles Hair, Hair Follicles, Sebaceous Glands, Sweat Glands, and Nails Integumentary accessory structures Derived from embryonic epidermis Located in dermis Project through the skin surface Human Body o The human body is covered with hair, except: Palms Soles Lips Portions of external genitalia Functions of Hair o Protects and insulates o Guards openings against particles and insects o Is sensitive to very light touch The Hair Follicle o Located deep in dermis o Produces nonliving hairs o Wrapped in a dense connective tissue sheath o Base is surrounded by sensory nerves ( root hair plexus) Accessory Structures of Hair o Arrector pili – involuntary smooth muscle Causes hairs to stand up Produces “ goose bumps” – contraction pulls hair follicle, forcing hair to stand up o Sebaceous glands Lubricate the hair Control bacteria Regions of the Hair o Hair root – lower part of the hair Attached to the integument o Hair shaft – upper part of the hair Not attached to the integument As hair is produced, it iskeratinized o Medulla contains flexible soft keratin o Cortex and cuticle contain stiff hard keratin Hair Shaft Structure o Medulla: the central core o Cortex: the middle layer o Cuticle: the surface layer Hair Production o Begins at the base of a hair follicle, deep in the dermis The hair papilla contains capillaries and nerves, surrounded by hair bulb The hair bulb produces hair matrix A layer of dividing basal cells Produces hair structure Pushes hair up and out of skin Hair Color o Produced by melanocytes at the air papilla Located at the hair bulb of the hair root Different forms and amount of melanin produce different colors o Determined by genes, influenced by hormonal and environment Types of Hairs o Vellus hairs Soft, fine Cover body surface o Terminal hairs Heavy, pigmented Head, eyebrows, and eyelashes Other parts of body after puberty Sebaceous Glands and Sweat Glands Exocrine Glands in Skin o Sebaceous Glands (oil glands) Holocrine glands Secrete sebum o Two Types of Sweat Glands Apocrine glands Merocrine (eccrine) glands Watery secretions Types of Sebaceous (Oil) Glands o Simple branched alveolar glands Associated with hair follicles o Sebaceous follicles Discharge directly onto skin surface Sebum – contains lipids and other ingredients, functions to: Lubricate and protect the epidermis Inhibit bacteria 1 Apocrine Sweat Glands o Found in armpits, around nipples, and groin o Secrete products into hair follicles o Produce sticky, cloudy secretions o Break down of secretion by bacteria causes odors o Surrounded by myoepithelial cells Squeeze apocrine gland secretions onto skin surface In response to hormonal or nervous signal o Note: even though these are named apocrine sweat glands, they actually release their contents by merocrine mode of secretion 2 Merocrine (Eccrine) Sweat Glands o Widely distributed on body surface, especially on palms and soles o Coiled, tubular glands o Discharge directly onto skin surface o Participates in sensible perspiration Water, salts, and organic compounds released o Functions to: Excrete water and electrolytes Cool skin Flush microorganisms and harmful chemicals from skin Other Integumentary Glands o Mammary glands: produce milk o Ceruminous glands: produce cerumen (earwax); protect the eardrum Control of Glands o Autonomic nervous system (ANS) Controls sebaceous and apocrine sweat glands Works simultaneously over entire body o Merocrine sweat glands Controlled independently Sweating occurs locally (ex. Sweaty palms, etc) o Thermoregulation The main function of sensible perspiration Works with cardiovascular system Regulates body temperature Nails o Protect fingers and toes o Made of dead cells packed with keratin o Metabolic disorders can change nail structure Ex. Respiratory disorders, AIDS, thyroid gland problems o Nail Production Occurs in a deep epidermal fold near the bone called the nail root Repair of the Integument Following an Injury Bleeding occurs Mast cells trigger inflammatory response A scab stabilizes and protects the area Germinative cells migrate around the wound Macrophages clean the area Fibroblasts and endothelial cells move in, producing granulation tissue (combination of blood clot, fibroblasts, and capillary network) Fibroblasts produce scar tissue o Inflammation decreases, clot disintegrates o Fibroblasts strengthen scar tissue o A raised keloid may form – thickened raised scar tissue (harmless) Note: scar tissue that forms is not the same as original tissue. o Keloid forms when scar tissue formation continues past the point of normal tissue repair. Importance of the Integumentary System Protects and interacts with all organ systems Changes in skin appearance are used to diagnose disorders in other systems Effects of Aging Epidermal thinning Decreased numbers of dendritic (Langerhans) cells Decreased vitamin D3 production Decreased melanocyte activity Decreased glandular activity (sweat and oil glands) Reduced blood supply Decreased function of hair follicles Reduction of elastic fibers Decreased hormone levels Slower repair rate Chapter 6: Osseous Tissue and Bone Structure An Introduction to the Skeletal system The Skeletal System includes: Bones of the skeleton (206 major bones in the body) Cartilages, ligaments and connective tissues Five Primary Functions of the Skeletal System Support – structural support for the whole body, attachment for soft tissues/organs Storage of minerals (calcium – most abundant mineral in the body) and lipids (yellow bone marrow – energy reserves) Blood cell production (occurs in the red bone marrow) Protection – skull protects brain, ribs protect heart/lungs, vertebrae protects spinal cord Leverage (force of motion) – allows body movement when skeletal muscles contract Classification of Bones: Bones are classified by: o Shape o Bone markings (surface features; marks) o Internal tissue organization (spongy/compact) Six bones shapes: o Sutural (wormian) bones: small, flat, oddly shaped bones Found between the flat bones of the skull. Vary in size. Borders are like pieces of a jigsaw puzzle – can be as small as a grain of sand to as wide as a quarter o Irregular bones: complex shapes with short, flat, notched, or ridged surfaces. The vertebrae that form the spinal column, the bones of the pelvis, and several bones in the skull o Short bones: small and thick; boxlike Ankle and wrist bones (Carpal bones, tarsal bones) o Flat bones: thin, parallel surfaces Roof of the skull, sternum, ribs, scapulae Provide protection for underlying soft tissues and offer an extensive surface are for the attachment of skeletal muscles o Long bones: long and slender Arm, forearm, thigh, leg, palms, sloes, fingers, toes o Sesamoid bones: small, round and flat, shaped like a sesame seed Develop inside tendons near joint of the knees, hands, and feet (ex. The patella is a sesamoid bone) Near joints at the knee, the hands and feet Vary in location and abundance Accounts for disparities in the total number of bonse in the body Bone Markings – surface features of a bone o Depressions, grooves, tunnels along bone surface Where blood and nerves lie along side or penetrate into bone Sulcus: narrow groove Fossa: shallow depression o Elevations or projections Where tendons and ligaments attach Where articulation with other bones occur Process: projection or bump Processes formed where tendons or ligaments attached – trochanter, crest, spine, line, tubercle, tuberosity Process formed where joints occur between adjacent bones: head, neck, facet, condyle, trochlea Ramus: extension of a bone that forms an angle with the rest of the structure Openings: sinus, foramen, fissure, meatus, canal Internal tissue organization o Structure of a long bone Diaphysis – the tubular shaft of the bone A heavy wall of compact bone, or dense bone A central space called medullary (marrow) cavity Epiphysis – wide part at each end Articulation with other bones Mostly spongy (cancellous) bone Covered with compact bone (cortex) Metaphysis – where the diaphysis and epiphysis meet o Structure of a flat bone Resembles a sandwich of spongy bones between two layers of compact bone Ex. The parietal bone of the skull o Within the cranium, the layer of ongy bone between the compact bone is called the ploe o Red bone marrow is located in the spongy bone, but bone does not contain a medullary cavity as seen in long bones Bone (Osseous) Tissue Bone tissue o Dense, supportive connective tissue o Contains specialized cells o Produces solid matrix of calcium salt deposits around collagen fibers Characteristics of bone tissue: o Dense matrix, containing: Deposits of alcium salts Osteocytes (bone cells) within cunae (chambers surrounded by the bone matrix) they are organized around blood vessels and connected to other osteocytes by gap junctions. o Canaliculi – small channels that connect lacunae to each other and to blood vessels of the central canal Form pathways for blood vessels for exchange of nutrients and wastes o Periosteum Covers outer surfaces of bones Consists of outer fibrous and inner cellular layers Bone matrix – composed of: o Minerals Twothirds of bone matrix is alcium phosphate , CA2(PO4)2 Reacts with calcium hydroxide , Ca(OH)2 to form crystals of hydroxyapatite, Ca10(PO4)6(OH)2 Hydroxyapatite incorporates other lcium salts (CaCO3) and ions (sodium, magnesium, fluoride) Matrix proteins Onethird of bone matrix is protein fibers (agen) o Bone matrix of calcium crystals and protein allow for bone to be strong and still somewhat flexible Bone cells – make up only 2 percent of bone mass: o Bone contains four types of cells Osteocytes: mature bone cell that maintains the bone matrix Live in lacunae between layers (lamellae of matrix Connected by cytoplasmic extensions through canaliculi in lamellae by gap junctions Do not divide Two major functions of osteocytes o To maintain protein and mineral content of the matrix o To help repair damaged bone Osteoblasts: immature bone cell that secretes osteoid, the organic component of bone matrix (osteogenesis) Osteoid – the matrix produced y osteoblasts, but not yet calcified by calcium salts to form bone When osteoblasts become surrounded by bone, they become osteocytes Osteoprogenitor cells: stem cell who’s divisions produce osteoblasts Mesenchymal stem cells that divide to produce osteoblasts Located in: o Endosteum – lines the medullary cavity and passageway for blood vessels found in the matrix of compact bone o The inner cellular layer of iosteum Important in fracture repair Osteoclasts: multinucleated cells that secretes acids and enzymes to dissolve bone matrix Derived from stem cells that produce acrophages o Do not develop from o steoprogenitor cells Secrete acids and proteindigesting enzymes o Dissolve bone matrix and release stored minerals (osteolysis/resportion) o Important in regulating calcium and phosphate concentrations in body fluids Homeostasis: o Bone building (by steoblasts and bone recycling (by steoclasts must balance More breakdown than building, bones become weak Exercise, particularly weightbearing exercise, causes osteoblasts to build bone faster than osteoclasts can break down bone This can be a problem for astronauts Compact Bone and Spongy Bone o The structure of compact bone o Osteon is the basic unit of mature compact bone Osteocytes concentric lamellae central are arranged in around a canal containing blood vessels o Perforating canals Perpendicular to the ntral cana Carry blood vessels into bone and marrow o Circumferential lamellae Lamellae wrapped around the long bone, encircling multiple osteons osteons Binds together o The structure of spongy bone o Does not have osteons o The matrix forms an open network of rabeculae bone fiber bundles o Trabeculae have o blood vessels, canaliculi open onto surface of trabeculae o The space between trabeculae is filled with bone marrow Which has blood vessels And supplies nutrients to eocytes Forms red blood cells o Yellow bone marrow – found in medullary cavity and in spongy bone of some bones Is yellow because it stores fat ose tissue) o Compact bone is covered with a membrane o Periosteum on the outside Covers all bones except parts enclosed in joint capsules Made up of an outer, fibrous layer and an inner, cellular layer Perforating (Sharpey’s) fibers: collagen fibers of the periosteum Connect with collagen fibers in bone and with fibers of joint capsules; attach tendons and ligaments Strengthens tendon and ligament attachment to bone Functions of eriosteum Isolates bone from surrounding tissues Provides a route for circulatory and nervous supply Participates in bone growth and repair o Endosteum on the inside An incomplete cellular layer: Lines the medullary (marrow) cavity Covers trabeculae of spongy bone Lines central canals Contains osteoblasts, osteoprogenitor cells, and osteoclasts Is active in bone growth and repair Bone Formation and Growth Bone development o Human bones grow until about age 25 o Osteogenesis – bone formation o Ossification – the process of replacing other tissues with bone o Fibrodysplasia ossificans progressive (FOP) – rare genetic disease Bone forms in the wrong places (heterotropic bones ) after minor injuries, replacing muscle tissue, etc. Treatment can be problematic because surgical removal can trigger more ossification Bone development o Calcification – the process of depositing calcium salts Occurs during bone ossification and in other tissues ( Cartilage) o Ossification Two main forms of ossification Endochondral ossification Intramembranous ossification 1. Endocondral ossification a. Ossifies bones that originate as aline cartilage 1) Most bones originate as hyaline cartilage b. There are seven main steps in endochondral ossification 1) Enlargemen t of artilage and chondrocytes . Calcification of cartilage begins and chondrocytes die. Chondrocytes are cells that produce cartilage. 1. Matrix is reduced to a series of small struts that soon begin to calcify. 2. Enlarged chondrocytes die and disintegrate, leaving cavities within the cartilage 2) Blood vessels grow into shaft. Cells in ichondrium differentiate into osteoblasts – forms bone around shaft (diaphysis) 1. The shaft of the cartilage becomes ensheathed in a superficial layer of bone. 3) Fibroblasts migrate to “one” cente r and differentiate into osteoblasts to create the imary ossification center. Begins production of spongy bone 1. Blood vessels penetrate cartilage and invade central region 2. Fibroblasts migrate within blood vessels and begin producing spongy bone. 3. Bone formation spreads along the shaft towards the ends 4) Bone enlarges, osteoclasts appear and remove trabeculae in center of the diaphysis , creating dullary cavity (bone remodeling). Further growth increases length and diameter 1. Osseous tissue of the shaft become thicker and cartilage near each epiphysis is replaced by shafts. 5) Centers of epiphysis calcify, capillaries and osteoblasts enter area, forming secondary ossification centers 6) Epiphysis fills with spongy bone, leaving a thin cap of articular cartilage covering bone end. piphyseal cartilage (epiphyseal line in fully grown bones) at etaphysis separates diaphysis from epiphysis. On diaphysis side, steoblasts replace cartilage with bone (occurs at same rate as new cartilage production on epiphyseal side) 7) At puberty, cartilage production slows while osteoblast activity increases. Causes epiphyseal cartilage to become narrower and narrower until it disappears and longitudinal growth of bone stops. (epiphyseal closure) Appositional growth o Compact bone thickens and strengthens long bone with layers of circumferential lamellae o As bone growth occurs to the outer surface, osteoclasts remove bone matrix located at the inner surface (usually at a slower rate) causes enlargement of medullary cavity as the bone gets larger in diameter Epiphyseal lines o When long bones stop growing, after puberty: Epiphyseal cartilage disappears Is visible on xrays as an epiphyseal line Mature bones o as long bone matures: osteoclasts enlarge medullary (marrow) cavity osteons form around blood vessels in compact bone 2. Intramembranous ossification a. Also called dermal ossification (because it occurs in the dermis) 1) Produces dermal bones such as mandible (lower jaw) and clavicle (collarbone) and flat bones of the skull b. There are five main steps in ntramembranous ossification 1) Mesenchymal cells cluster and differentiate into osteoblasts. They secrete bone matrix components that crystallize with calcium salts 1. Starts about the eights week of embryonic development. 2. This type of ossification occurs in the deeper layer of the dermis, forming dermal bones 2) Some osteoblasts are trapped in the bone matrix and differentiate into osteocytes Bone grows (spicules) outward from the ossification center 3) Blood vessels enter the area bringing nutrients – bone growth accelerates. icules interconnect and trap blood vessels within the bone. 4) Osteoblasts close to blood vessels continue to deposit bone matrix, creating pongy bone surrounding the vessels. 5) Remodeling around blood vessels produces osteons. Osteoblasts on bone surface (along with connective tissue there) become the periosteum. Blood supply of mature bones o Nutrient artery and vein a single pair of large blood vessels enter the diaphysis through the nutrient foramen femur has more than one pair o metaphyseal vessels supply the epiphyseal cartilage where bone growth occurs o periosteal vessels blood to superficial osteons secondary ossification centers Lymph and Nerves o The periosteum also contains: networks of lymphatic vessels sensory nerves Bone Remodeling Process of remodeling o The adult skeleton: Maintains itself Replaces mineral reserves Recycles and renews bone matrix Involves osteocytes, osteoblasts and osteoclasts o Bone continually remodels, recycles and replaces o Turnover rate varies: If eposition is greater than removal, bones get stronger If emoval is faster than replacement, bones get weaker Exercise, Hormones and Nutrition Effects of exercise on bone o Mineral recycling allows bones to adapt to stress o Heavily stressed bones become thicker and stronger Bone degeneration o Bone degenerate quickly o Up to onethird of bone mass can be lost in a few weeks of inactivity produced by integumentary system Ex. Using a crutch for a few weeks will cause those leg bones to lose up to 1/3 of its mass. Normal Bone Growth and Maintenance Depend on Nutritional and Hormonal Factors o A dietary ource of calcium and phosphate salts plus small amounts of agnesium, fluoride, iron and manganese o The hormone calcitrol made in the kidneys, synthesis requires vmin D3 (cholecalciferol) helps absorb alcium (ca2+) and hosphorous (P) from digestive tract o Vitamin C is required for collagen synthesis and stimulation of osteoblast differentiation o Vitamin A stimulates osteoblast activity o Vitamin K and B12 help synthesize bone proteins o Growth hormone and thyroxine stimulate bone growth If GH increase occurs before puberty, gantism can occur. If after, bones get thicker and not longer (omegaly). Excessive cartilage formation at epiphyseal cartilage. Caused by gene mutation affecting connective tissue throughout the body. Can cause life threatening cardiovascular problems Genetic mutation in collagen fibers o Estrogens and androgens stimulate steoblasts o Calcitonin (decrease blood calcium) and arathyroid hormone (increases blood calcium) regulate calcium and phosphate levels Calcium Homeostasis The skeleton as acalcium reserve o Bones store calcium and other minerals o Calcium is the most abundant mineral in the body Calcium ions are vital to: Membranes Neurons Muscle cells, especially heart cells Calcium regulation o Calcium ions in body fluids must be closely regulated o Homeostasis is maintained By calcitonin and parathyroid hormone (PTH) Which controls storage, absorption and excretion Calcitonin and Parathyroid Hormone Control o Affect Bones: where calcium is stored Digestive tract: where calcium is absorbed Kidneys: where calcium is excreted Parathyroid hormone (PTH) pump up o Produced by parathyroid glands in neck o Increases calcium ion levels by: Stimulating steoclasts Increasing ntestinal absorption of calcium Decreasing calcium excretion at kidneys Calcitonin decreased calcium! o Secreted by cells (parafollicular ce in thyroid o Decreases calcium ion levels by: Inhibiting osteoclast activity Increasing calcium excretion at kidneys Fractures Fractures o Cracks or breaks in bones o Caused by physical stress Fractures are repaired in four steps o Bleeding Produces a clot (fracture hematoma) Establishes fibrous network Bone cells in the area die o Cells of the endosteum and periosteum Divide and migrate into fracture zone Calluses stabilize the break External callus of cartilage and bone surrounds break Internal callus develops in medullary cavity o Osteoblasts Replace central cartilage of external callus with spongy bone o Osteoblasts and osteocyte remodel the fracture for up to a year Initial swelling of fracture repair evident, however, remodeling reduces bone calluses Major types of fractures: o Transverse fractures – across the long axis o Displaced fractures – produce new/abnormal bone arrangements o Compression fractures – produced on vertebrae on hard falls to seat (often associated with osteoporosis) o Spiral fractures – twisting stress on length of bone o Compound fracture – bone fracture that breaks through the skin o Epiphyseal fractures – usually occurs where bone matrix is undergoing calcification, can permanently stop growth o Comminuted fractures – shatters bone into multiple fragments o Greenstick fractures – only one side of the bone is broken, other is bent generally occurs in children’s bones, not fully ossified o Colles fracture – break in distal portion of radius (usually caused by reaching out to cushion falls) o Pott’s fracture – occurs at ankle affecting tibia and fibula Effects of Aging on the Skeletal System AgeRelated Changes o Bones become thinner and weaker with age Osteopenia begins between ages 30 and 40 Women lose 8 percent of bone mass per decade; men lose 3 percent o The epiphyses, vertebrae, and jaws are most affected Resulting in fragile limbs Reduction in height Tooth loss Osteoporosis – severe bone loss o Affects normal function o Over age 45, occurs in 29 percent of women and 18 percent of men o Treatment: exercise (build up osteoblasts, slow own osteoclasts), sun exposure (vitamin D to absorb calcium) Hormones and Bone Loss o Estrogens and androgens help maintain bone mass o Bone loss in women accelerates after menopause Treatment: hormone replacement therapy (HRT) Cancer and Bone Loss o Cancerous tissues (bone, breast, and other tissue cancers) relase osteoclast activating factor That stimulates osteoclasts And produces severe osteoporosis Chapter 9 – Articulations An introduction to Joints • Articulations • Body movement occurs at joints (articulations) where two bones connect • Joint Structure • Determines direction and distance of movement (range of motion or ROM) • Joint strength decreases as mobility increases • The stronger the joint, then the joint = less mobile • The weaker the joint, then joint = more mobile Classification of joints: • Two Methods of Classification 1. Functional classification is based on range of motion of the joint 2. Structural classification relies on the anatomical organization of the joint Note: be careful distinguishing the difference between Functional and Structural classifications • Functional Classifications 1. Synarthrosis (immovable joint ) most stable • E.g. sutures 2. Amphiarthrosis slightly movable joint ) moderately stable 3. Diarthrosis (freely movable joint) least stable • E.g. joint in the shoulder, elbow, knee, etc. • Structural Classifications 1. Bony – synotoses (synarthroses) 2. Fibrous – sutures and gomphoses (synarthroses); syndesmoses (amphiarthroses) 3. Cartilaginous – synchondroses (synarthroses) and symphyses [e.g. connects the two coccyx bones together] (amphiarthroses) Synovial 4. – only diarthroses Note: the functional classifications of these structural classifications are in the parentheses • Synarthroses ( Immovable Joints ) • Are very strong • Edges of bones may touch or interlock • Four types of synarthrotic joints 1. Suture Bones interlocked • • Are bound by dense fibrous connective tissue • Are found only in skull 2. Gomphosis • Fibrous connection (periodontal ligament) • Binds teeth to sockets 3. Synchondrosis • Is a rigid cartilaginous bridge between two bones • Epiphyseal cartilage/plate of long bones • Between vertebrosternal ribs and sternum 4. Synostosis • Fused bones, immovable • Metopic suture of skull (fuses two sides of frontal bone) • Epiphyseal lines of long bones • Amphiarthroses • More movable than synarthrosis • Stronger than freely movable joint • Two types of amphiarthroses 1. Syndesmosis • Bones connected by ligaments (ex. Distal end of tibia and fibula) 2. Symphysis • Bones separated by fibrocartilage (ex. Pubic symphysis connects left and right coxal bones) • Synovial Jo nts Dia (hroses ) • Also called movable joints • At ends of long bones • Enveloped Within articular c psules • Lined with synovial membrane – not a true epithelial membrane; has cells called synoivalcytes that produce synoival fluid that lubricates the cavity, so the bones can articulate smoothly (provides protection against friction) Synovial Joints • Articular Ca tilages • Pad articulating surfaces within articular c psules • Prevent bones from touching • Smooth surfaces lubricated by synovial f uid • Has consistency of heavy molasses • Functions to reduce friction • Excessive exercise can damage bones if sufficient synovial fluid is not generated. • Synovial Fl id • Contains slippery proteoglycans secreted by fibroblasts • Resembles interstitial fluid, not much in joint (ex. Knee joint only has up to 3 mL of fluid) • Functions of synovial fluid • Lubrication – articular cartilage act as sponge filled with fluid. Compression of it pushes some fluid out. • Nutrient distribution – fluid circulates as joint moves, provides nutrients to chondrocytes in area • Shock absorption – viscocity of fluid increases with increased pressure • Accesory Structures • Cartilages • Cushion the joint • Fibrocartilage pad called a meniscus (orarticular disc ; plural, menisci ), located between opposing bones in synovial joint • Fat ads • Adipose tissue superficial to the joint capsule • Protect articular cartilages • Outside the articular capsule (helps hold it in place) • Ligaments – continuous with periostea of articulating bones (no direct blood supply) • Support, strengthen joints • Sprain – ligaments with torn collagen fibers • Due to lack of blood supply, repair of ligaments can take time • Tendons • Attach to muscles around joint • Help support joint • Cover over the synoval joint to help stabilize the joint. • Bursae • Singular, bursa , a pouch • Pockets of synovial fluid, lined by synovial membrane • Cushion areas where tendons or ligaments rub • Bursitis – inflamed bursae causing pain, can result from repetitive motion, irritation, trauma, infection (ex. Bunion) • Factors That Stabilize Synovial Joints • Prevent injury by limiting range of motion • Collagen fibers (joint capsule, ligaments) • Shape of the articulating surfaces and menisci • Presence of other bones, muscles, or fat pads • Tension in the tendons of articulating bones • Note: pain receptors are not found on the inside of synovial joints. Pain felt due to joint damage results from nerves that monitor the capsule, ligaments, and tendons • Ever wonder why your knee does not bend forwar
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