Histology Test 1
Terms
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- can develop from endoderm, mesoderm, or ectoderm
- Epithelia
- 1. Epithelial Membranes (Epithelia) 2. Epithelial Glands
- 2 Major Divisions of Epithelial Tissue
- continuous sheets of cells that cover outer surfaces or line internal surfaces; attach to connective tissue by basement membrane; cells are joined as cell junctions; do not contain blood vessels
- Epithelial Membranes
- Epithelial Glands
- Develop when epithelia invaginate into underlying connective tissue
- How do nutrients and oxygen reach epithelial membranes?
- By diffusing from blood vessels in connective tissue beneath the basement membrane
- Functions of epithelia
- 1. Protection (skin) 2. Absorption (intestinal lining) 3. Secretion(stomach lining)
- Types of epithelia
- 1. simple (1) 2. Stratified (2 or +) 3. Pseudostratified (1; appears stratified b/c cells are different heights; all cells are in contact with basement membrane)
- Simple Epithelia
- 1. squamous (single, flattened) 2. Simple cuboidal (single, cube-shaped) 3. Simple columnar (tall, column-shaped)
- mesothelium of body cavities, endothelium of blood vessels
- Example of simple squamous
- collecting tubules of kidney
- Example of simple cuboidal
- Often contains absorptive cells interspersed with secretory cells; small intestine, stomach lining
- Example of simple columnar
- goblet cells secrete mucus; absorptive cells have microvilli on luminal surface which facilitate nutrient absorption; microvilli give rise to striated border (light microscopy)
- Simple columnar in small intestine
- columnar cells may be ciliated with goblet cells interspersed between
- Some parts of the lower respiratory tract
- all columnar cells are mucus-secreting
- Stomach lining
- Simple Epithelia functions
- absorption and secretion
- Stratified epithelia function
- protection
- Stratified Epithelia
- 1. Stratified Squamous (multiple, outermost-squamous) 2. Stratified cuboidal (2 or 3, cuboidal) 3. Stratified columnar (several;, outermost-columnar) 4. Transitional (multiple, outermost-large rounded cells:often polyploid of binucleate)
- Examples of Stratified Squamous
- 1. nonkeratinized (lining of vagina) 2. keratinized (skin epidermis)
- Rare; Large ducts
- Example of stratified columnar
- lining of urinary bladder
- Example of transitional
- lining of large ducts
- Example of stratified cuboidal
- taller-either ciliated or goblet; shorter-basal, serve as stem cells for others
- Pseudostratified ciliated columnar
- lines most of upper respiratory tract
- Example of pseudostratified ciliated columnar
- ductus epididymis; lack true cilia; have nonmotile stereocilia; lacks goblet cells
- Example of pseudostratified columnar
- Types of Cell Junctions
- 1. tight junctions (only in epithelia) 2. adhering junctions 3. gap junctions
- zonula occludens (tight junction)
- forms a belt around cell perimeter near apical luminal) surface
- forms a complete, tight seal; prevents passage of material across the epithelium (e.g. macromolecules are prevented from passing from intestinal lumen into intercellular space)
- zonula occludens
- tight junction that is restricted to specific area of cell perimeter forming an incomplete seal
- fascia occludens
- Example of fascia occludens
- endothelium of blood vessels
- Zonula adherens (adhering junctions)
- belt-like junction around perimeter of cell; located just below zonula occludens on lateral aspect of contiguous cells; intercellular gap-filled with filamentous material
- site of attachment for circumferential band of microfilaments located just deep to the membrane
- zonula adherens
- cells are joined as cell junctions; do not contain blood vessels
- Epithelia
- desmosome
- macula adherens
- small, circularjunction just below zonula adherens; series of button-like junctions, uneven row
- macula adherens
- seen on either side of opposed membranes
- electron-dense plaques
- serve as attachment sites for bundles of tonofilaments (intermediate filament)
- plaques
- between two plaques
- fine electron-dense line; transmembrane linkers that extend across intercellular gap
- seen between epithelial cells and basement membrane
- hemidesmosomes (half-desmosomes)
- Junctional complex (electron microscope)
- zonula occludens, zonula adherens, and macula adherens
- junctional complex (light microscope)
- terminal bar
- communications junctions; small circular regions of opposed cell membranes bridged by connexons
- Gap Junctions (Nexuses)
- Functions of gap junctions
- permit direct cell-to-cell transfer of low molecular wt. nutrients and intracellular messengers (cAMP) and maintain electrical coupling b/w cells
- tiny tubular channels that allow passage of ions and various small molecules from cell-to-cell; represent transmembrane proteins that interlock across the narrow gap
- Connexons
- beneath striated border of intestinal epithelial cells; horizontal network of microfilaments, intermediate filaments, spectrin, and some myosin
- Terminal web
- 2 Types of Epithelial Glands
- 1. exocrine 2. endocrine
- Components of exocrine glands
- 1. groups of specialized cells-secretory units; produce characteristic secretions 2. tubular ducts- convey secretions onto an epithelially-covered surface
- Exocrine Gland classification
- 1. simple-single, unbranched duct 2. compound-branched duct system
- example of simple gland
- sweat gland
- example of compound gland
- pancreas
- Secretory gland shapes
- 1. tubular gland- (tube-shaped) 2. alveolar (acinar) gland- rounded 3. tubuloalveolar gland- both types
- secretes enzymes in a watery fluid
- serous gland
- secrets a viscous glycoprotein called mucus
- mucous gland
- both types of secretions are produced
- mixed (seromucous gland)
- example of serous gland
- parotid gland
- example of mucous gland
- sublingal gland
- example of mixed (seromucous) gland
- submandibular gland
- (H&E) base contains large,spherical nucleus; cytoplasm-intensely basophilic due to RER abundance; apical-numerous eosinophilic granules filled with secretory enzymes
- serous cell
- (H&E) base-flattened nucleus;cytoplasm-pale and vasculated due to abundance of secretory granules containing mucin
- mucous cells
- mucin
- visualized by PAS-stain; becomes hydrated when released from cell to form mucus
- mostly mucous cells with a small "cap" of of serous cells-serous demilume
- mixed secretory units
- processes that surround each secretory unit and cradles them; contraction expels secretions into the duct system
- myoepithelial cell
- secretion occurs via exocytosis; most common method
- merocrine gland
- example of merocrine gland
- pancreas
- entire cell and its contents form secretory product
- holocrine gland
- example of holocrine gland
- sebaceous gland- cells in basal portion are displacedinto interior region as new cells arise in lining layer, displaced cells degenerate and accumulate lipid, disintegrated emerge as oily sebum
- apical portion of cell membrane and associated cytoplasm are expelled as secretory product (possibly incorrect; now known to secrete via merocrine)
- apocrine gland
- example of apocrine gland
- mammary gland
- 2 major components of exocrine glands
- 1. parenchyma- epithelial; secretory units and ducts 2. stroma-connective; gland, blood vessels, and nerves
- connective tissue that encloses exocrine gland
- capsule
- consists of fibrous connective tissue, continuous with the capsule, subdivides the parenchyma into lobes (large) or lobules (small)
- Septa
- Intralobular ducts
- lie within the parenchyma of the lobules; empty into interlobular ducts
- Pathway for exocrine secretion
- alveolus-> intercalated duct-> intralobular duct ->interlobular duct -> main duct
- Exocrine secretion control
- regulated by nerve impulses from ANS (both) and certain hormones
- no ducts; secrete hormones directly into bloodstream that produces effects in distant tissue; surrounded by connective tissue capsule
- endocrine glands
- regulation of endocrine secretion
- negative feedback
- Loose Connective tissue
- areolar tissue; binds and nourishes other tissues
- made of intercelluar matrix (various fibers and ground substance) and cells
- Loose Connective Tissue
- 3 types of fibers in intercellular matrix
- collagen, reticular, and elastic
- Type I collegen
- collagen fibers
- exhibit axial periodicity
- collagen and reticular fibers
- synthesized by fibroblasts in loose connetive tissue
- type I collagen and type III collegen
- 1st step of collagen synthesis
- formation of alpha-chains in RER
- Alpha chains contain a high % of?
- glycine, proline, hydroxyproline, and hydroxylysine
- What determines collagen type?
- amino acid sequence
- 3 alpha chains form?
- 1 procollagen molecule
- Procollagen
- passes through Golgi and transports to cell membrane thru secretory vesicles before discharging
- How are collagen molecules yielded?
- procollagen peptidase cleaves off short peptide sequences from both ends and yields collagen(tropocollagen) which spontaneously assemble into collagen fibrils
- branching pattern; form a supporting network in myeloid and lymphoid tissues
- reticular fibers
- Type III collagen fibers
- reticular fibers
- produced by reticular cells in myeloid and lymphoid tissues
- reticular fibers
- PAS-positive; fibers are visible with silver stain
- Reticular cells
- Exhibit no axial periodicity
- Elastic fibers
- can be distinguished from other fibers when strained with orcein
- elastic fibers
- produced by fibroblasts in connective tissue
- elastic fibers
- precusor protein in elastic fibers? contains which amino acids?
- elastin; desmocine and isodesmocine
- a glycoprotein secreted by fibroblasts
- fibrillin (in the form of fine microfibrils)
- ground substance?
- macromolecular (principally glycosaminoglycans-repeating disaccharides) meshwork with a large V of tissue fluid
- What synthesizes glycosaminoglycans in loose connective tissue?
- fibroblasts
- proteoglycan
- when sulfated glycosaminoglycans become covalently attahced as side chains to axial core proteins
- principal unsulfated glycosaminoglycan in ground substance
- hyaluronic acid
- proteoglycans can be stained with?
- basophilia and metachromasia
- How do glycoproteins differ from proteoglycans?
- 1. carbohydrate moiety is not made of repeating dissacharides 2. protein component predominates
- when blood passes through a capillary
- hydrostatic pressure is greater at arterial end than venous end
- contains dissolved gases and nutrients
- interstitial fluid
- has a lower osmotic pressure than blood; contains small amount of colloidal protein
- tissue fluid
- where tissue fluid is produced
- arterial end of the capillary
- where tissue fluid is resorbed
- vemous end of capillary
- lymph
- fluid that collects in lymphatic capillaries
- edema (swelling)
- imbalance between production and removal of tissue fluid leading to an accumulation of fluid within affected tissues
- Causes of edema
- venous obstruction, lymphatic obstruction, increased capillary permeability, and decreased vascular protein
- e.g. congestive heart failure
- venous obstruction-impaired venous return->back pressure in capillaries->increases hydrostatic pressure and plamsa leakage
- e.g. post-surgical trauma
- backage of lymphatic capillaries->decrease in removal of excess tissue fluid
- e.g. allergic inflammation
- formation of gaps b/w endothelial cells in capillary wall->increase plasma leakage
- e.g. liver failure
- decreased vascular protein- reduction of colloiday protein->lower osmotic pressure->tissue fluid return reduction
- middle part of basement membrane
- lamina densa
- what lamina densa consists of
- laminin-5, type IV collagen (lacks axial periodicity), and proteoglycans
- product of the cells to which the basement membrane attaches
- lamina densa
- top part of basement membrane
- lamina lucida
- integrins
- chords that extend from lamina densa to cell membrane; composed of extracellular portions of cell adhesion molecules
- lower level, next to basment membrane
- lamina fibroreticularis
- layer of basement membrane that contains reticular fibers(type III) and type IV collagen fibers
- lamina fibroreticularis
- proteins in basement membrane that anchor cells to basement membrane
- laminin and fibronectin
- Where are basement membranes found?
- loose connective tisuue, muscle fibers, peripheral nerve fibers, endothelial mast cells, and fat cells
- window-like openings in edothelial cells covered by a thin diaphragm
- fenestrae
- fenestrated capillaries
- extra-permeable vessels
- continuos capillaries
- lack fenestrations
- external to endothelium of capillaries and venules; insinuated in basement membrane
- pericytes
- pericytes
- represent pluripotent cells that can produce new fibroblasts, smooth muscle cells, and endothelial cells
- retain some of the potentiality associated with undifferentiated mesenchymal cells in embryo
- pericytes
- responsible for formation of scar tissue in fibrosis
- fibroblasts
- mature fibroblast
- fibrocyte
- a result of mature fibroblasts rarely dividing is?
- new fibroblasts derive from pericytes
- large phagocytic cells that form part of the mononuclear phagocyte system
- macrophages
- macrophages in loose connective tissue
- histiocyte
- multinucleated cells
- foreign body giant cells
- produced by plasma cells and can combine with antigens
- antibodies
- derived from certain lymphocytes and do not divide
- plasma cells
- large rounded cells that contain numerous granules that contain histamine and heparin
- mast cells
- rich capillary supply and abundance of mitochondria
- brown fat
- primary function is to metabolize triglycerides and generate body heat
- primary function of body fat
- most adipose tissue (10-20% in males and 15-25% in females)
- white fat
- synthesis, storage, and mobilization of triglycerides and provides thermal insulation
- primary function of white fat
- 2 kinds of adipose tissue
- white fat and brown fat
- What provides an efficient store of fuel for cellular metabolism?
- high colorie content of triglycerides
- collagen fibers are oriented in the same direction
- dense regular connective
- e.g. of dense connective tissue
- ligaments, tendons, and aponeuroses
- collagen fibers are oriented in different directions
- dense irregular connective
- e.g. of dense irregular connective tissue
- dermis of the skin and capsule of numerous organs
- cells found in loose connective tissue
- lymphocytes and eosiniphils
- cartilaginous rings in the trachea and costal cartilage connecting ribs to the sternum
- extraskeletal cartilage
- found in articulating joints, where it provides a smooth, gliding surface at ends of articulating bones
- articular cartilage
- contains a few collagen fibers
- hyaline cartilage
- contains many collgen fibers
- fibrocartilage
- contains many elastic fibers
- elastic cartilage
- examples of hyaline cartilage
- tracheal rings, costal cartilage, articulating surfaces in joints
- cartilage consists of intercellular matrix, in which numerous chondrocytes are embedded; pearly-white
- hyaline cartilage
- perichondrium
- fibrous connective tissue that surrounds sites in the body where cartilage will form
- cells of the outer layer of the perichondrium
- fibroblasts that produce collagen fibers (fibrous layer)
- cells of the inner layer of the perichondrium
- chondroblasts that produce cartilage matrix (chondrogenic layer)
- after chondroblasts become surrounded by matrix they become?
- chondrocytes
- spaces in which chondrocytes live
- lacunae
- lacuna with a single chondrocyte
- primary lacuna
- chondrocyte that divides and produces daughter cell that resides in same lacuna
- secondary lacunae
- cell nest
- formed by parent and daughter chondrocytes
- cartilage growth from the inside out
- interstitial growth
- formation of cartilage by chondroblasts at the surface
- appositional growth
- perichondrium is absent in adults in?
- articular surfaces
- cartilage matrix
- amorphous gel that contains large amounts of proteoglycans and type II collagen fibrils
- produced by chondrocytes?
- collagen and proteoglycans
- What can bind a substantial amount of water in the matrix due to the particular macromolecular arrangement of the matrix?
- proteoglycans
- Monomers of ? attach to hyaluronic acid through?
- proteoglycans; link proteins
- proteoglycan aggregate
- intermingles with collagen fibrils
- 2 reasons why proteoglycans can bind considerable amounts of water
- 1. many interstices b/w sulfated glycosaminoglycan side chains 2. there are many negative charges to hydrogen bond water molecules
- cartilage matrix that immediately surrounds the lacunae; has a high concentration of sulfated glycosaminoglycans
- territorial or capsular matrix
- interterritorial matrix
- stains less intensely than territorial matrix
- capsular region
- metachromatic and PAS-positive
- How do chondrocytes within the matrix receive nutrients?
- diffusion that is possible b/c of large volume of water trapped within matrix
- examples of fibrocartilage
- intervertebral discs and tendon insertions into cartilage
- chondrocytes are arranged in longitudinal rows between bundles of type I collagen fibers
- fibrocartilage
- between chondrocytes, matrix is similar to capsular matrix of hyaline cartilage
- fibrocartilage
- perichondrium is absent in adult
- fibrocartilage
- examples of elastic cartilage
- external ear and epiglottis
- designed to withstand repeated bending
- elastic cartilage
- matix contains numerous elastic fibers and type II collagen fibrils
- elastic cartilage
- living cells embedded in an intercellular matrix in bone; occupy lacunae
- osteocytes
- contains more collagen than cartilage and is heavily mineralized with calcium salts
- intercellular matrix of bone
- Both bone and cartilage contain a fibrous connective tissue covering; in bone it is?
- periosteum
- highly vascularized
- bone
- canaliculi
- fine channels that are part of the vasular nature of bone; radiate outward from lacunae
- extend into regions where oxygen and nutrients are in greater supply
- osteocyte processes
- Why are osteocytes unable to divide?
- because the intercellular matrix becomes mineralized soon after it is produced
- How do all bones grow?
- By apposition-depostion of bone on preexisting surfaces
- intramembranous ossification
- occurs directly in vascularized mesenchyme
- endochondrial ossification
- occurs indirectly by replacing a cartilage model
- forms several flat bones of the cranium, as well as the mandible nd the clavicles
- intramembranous ossification
- mesenchymal cells
- exhibit long, interconnected processes in developing embryo
- What cells differentiate into osteoblasts and begin laying down intercellular matrix?
- mesenchymal cells
- when mesenchymal cells are surrounded by matrix they are called?
- osteocytes
- narrow spaces when filled with cytoplasmic processes of osteocytes
- caniculi
- after matrix is secreted...?
- it begins to calcify
- spicule
- first piece of newly formed bone that exhibits an irregular shape
- trabecula
- when osteoblasts deposit more matrix onto the surface of the spicule, it enlarges
- spongy (cancellous) bone
- latticework structure; continued groth that leads to a network of trabeculae
- appositional growth
- osteoblasts on the surface of the trabeculae continue to lay down bone matrix
- osteoclasts
- resorbs bone; have the capacity to erode bone surfaces
- osteoblasts
- deposit matrix on surface of the spicule
- bone remodeling
- combination of bone deposition and resorption; eventually converts spongy bone to compact bone
- osteogenic cells
- have potential to become osteoblasts; line inside channels
- osteon (haversian system)
- concentric layers of lamellae of bone with cental haversian canal
- represents the basic structural unit of compact bone
- osteon (haversian system)
- immature bone
- first type of bone to be produced in prenatal life
- have a higher concentration of osteocytes than mature bone
- immature bone
- woven bone
- collagen fibers run in various directions in the matrix
- coarsely-bundled bone
- collagen fibers are arranged into think, parallel bundles in the matrix
- fine-fibered or lamellar bone
- mature bone
- mature bone
- presence of lamellae; orientation of collagen fibers is at right angles to adjacent lamella
- Where osteogenic cells located?
- periosteum(covers outer surface of bone) and endosteum (lines internal surfaces of bone)
- examples of endosteum
- cental canals, marrow cavities, and spaces of spongy bone
- periosteum
- outer fibrous layer and inner osteogenic layer
- endosteum
- osteogenic layer
- when osteogenic cells proliferate they form?
- osteoblasts (vascularized regions) or chondroblasts (avascular regions)
- nondividing cells
- osteoblasts
- primary function is to form the organic constituents of bone matrix
- osteoblasts
- participate in the mineralization of bone matrix
- osteoblasts
- lower proteoglycan content and holds less water than cartilage matrix
- bone matrix
- type i collagen content is higher here?
- bone matrix
- calcification
- deposition of insoluble calcium salts in the bone matrix
- osteoid
- new bone matrix that has not yet been calcified
- calcification front
- interface between osteoid zone and clacified bone
- matrix vesicles
- cell derived structures that are thought to initiate matrix calcification; found lying free in matrix; contain alkaline phosphatase
- primary mineral component of bone (70% of wet weight)
- hydroxyapatite
- whenever osteoblasts are surrounded by bone matrix; nondividing
- osteocytes
- What interconnects neighboring osteocytes?
- gap junctions
- 2 functions of osteocytes
- 1. maintain bone matrix 2. release calcium from bone matrix
- nondividing, motile, multinucleated cells; resorb bone matrix
- osteoclasts
- derived fom monocytes
- osteoclasts
- Howship's lacunae or resorption bays
- where some osteoclasts lie; recesses of bone surface
- ruffled border
- branching, finger-like processes that extend from osteoclast membrane onto the bone surface; represents portion of osteoclast activity resorbing bone
- where are secretory vesicles containing hydrolytic enzymes released by exocytosis?
- ruffled border
- secretes organic acids to bring about local decalcification of bone matrix
- ruffled border
- possible participants in bone resorption
- fibroblasts (secrete collagenase and phagocytose collagen fragments) and macrophages
- Parathyroid hormone
- raises blood calcium
- calcitonin
- lowers blood calcium
- vitamin D metabolite
- raises blood calcium
- hypercalcemia
- too high blood calcium levels
- hypocalcemia
- too low blood calcium levels
- major site of action for PTH, CT, and vitamin D metabolite
- osteoclast
- stimulate bone resorption by osteoclasts
- PTH and vitamin D metabolite
- inhibits bone resorption by osteoclasts
- CT
- How do tubular bones form?
- ossification of a temporary cartilage model (endochondrial ossification)
- osteoporosis
- net bone loss due to imbalance b/w bone formation and bone resorption; results in predisposition to bone fractures
- rickets
- caused by insufficient vitamin D; poor calcification of bone, which leads to skeletal deformities in infants
- osteomalacia
- rickets in adults
- Why is vitamin D required?
- for proper osteoclast activity and proper gut absorption of calcium and phosphate
- scurvy
- caused by insufficient vitamin C; results in decreased thickness of bone cortex and a corresponding fragility of the bone
- Why is vitamin C (ascorbic acid) required?
- collagen synthesis
- 3 factors that adversely affect bone formation
- 1. interference with organic matrix secretion 2. interference of matrix calcification 3. imbalance b/w bone formation and bone resorption
- nutrient artery (derived from the periosteal bud)
- enters medullary cavity thru wall of diaphysis; principal blood supply to a long bone
- Where does supplemental blood supplies to bone come from?
- periosteal artery, epiphyseal artey, and the metaphyseal artery
- metaphyses
- flared regions of long bones b/w epiphyses and diaphysis
- What is present in Haversian canals?
- a small arteriole, and venule, sometimes a single capillary, some nerves, NO LYMPHATICS
- Zone of resting cartilage
- no proliferation of chondrocytes; appearance is typical of hyaline cartilage
- Zone of proliferating cartilge
- chondrocytes are proliferating and are seen arranged in longitudinal rows of lacunae
- zone of maturing cartilage
- chondrocytes hypertrophy and produce large amounts of alkaline phosphatase for matrix vesicles
- zone of calcifying cartilage
- cartilage matrix becomes calcified and begins to break down; capillaries form medullary cavity below; osteogenic cells->osteoblasts and deposit bone matrix on remnants of calcified cartilage forming bony trabeculae with cores of calcified cartilage; formation of osteons in diaphysis; periosteum forms layers of bone outside of diaphysis; bone is remodeled
- What is the adult structure of bone?
- outer and inner diaphysis are covered by outer and inner circumferential lamellae which enclose compact bone; compact bone (cortex) consists of osteons and interstitial lamellae; Longitudinally b/w each osteon-> haversian canal; tranverse connections b/w are due to vessels running in Volmann's canals; spongy bone-inner diaphysis, surrounds medullary cavity; epiphysis-interior-spongy bone
- secondary ossification centers
- after birth; form in apiphyses; only in long bones; bone replaces cartilage on articular surfaces of joints and as a epiphyseal plate b/w epiphyses and diaphyses; in adult, epiphyseal plate->bone
- Formation of cartilage model
- mesenchymal cells differentiate into chondroblasts that eventually form a model consisting of hyaline cartilage surrounded by perichondrium; model grows by interstitial and appositional growth of cartilage
- Formation of primary ossification center
- at midsection, Ca salts deposit and impede diffusion; chondrocytes die or are altered; cartilage matrix breaks down; cells of inner layer of perichondrium->osteoblasts and produce bone matrix; perichondrium is now periosteum; subperiosteal vone surrounds midsection; blood vessels and osteogenic cells (periosteal bud) grow to interior of cartilage; osteogenic cells->osteoblasts that deposit bone matrix on calcified cartilage; region in midsection is primary cos
- Formation of epiphyses and diaphysis
- spongy bone forms when trabeculae contain cores of calcified cartilage; center is resorbed forming medullary cavity
- Where is muscle tissue derived from?
- mesoderm
- 3 different kinds of muscle
- skeletal, cardiac, and smooth
- skeletal muscle
- striated and voluntary
- cardiac muscle
- striated and involuntary
- smooth muscle
- nonstriated and involuntary
- muscle that elicits movement of the skeleton
- skeletal muscle
- found in the heart
- cardiac muscle
- found in the walls of the blood vessels and various hollow organs
- smooth muscle
- 3 layers of skeletal muscle
- epimysium, perimysium, and endomysium
- epimysium
- surrounds entire muscle
- perimysium
- continuous with epimysium; surrounds bundles of muscle fibers
- fascicles
- bundles of muscle fibers in perimysium
- endomysium
- continuous with perimysium; surrounds individual muscle fibers; contains capillaries and nerve fibers that supply muscle fibers
- all connective tissue merge to form?
- e.g. tendons, aponeuroses
- muscle fibers
- cells of skeletal muscle
- sarcolemna
- cell membvrane of muscle fibers
- sarcoplasm
- cytoplasm of skeletal fibers
- A-bands
- dark bands in muscle fibers
- H-zone
- pale region in middle of A-band (dark)
- I-bands
- light staining bands in muscle fibers
- Z-line
- thin line that bisects I-bands
- myofibrils
- causes striated pattern; has same banding pattern as muscle fiber
- sarcomere
- segment of myofibril from Z-line to Z-line; contractile unit of striated muscle
- myofilaments
- thin(actin) and thick (myosin)
- only thin filaments connected at one end to the Z-line
- I-band
- thick filaments and overlapping thin filaments that extend
- A-band
- region of A-band where thin filaments do not extend; only thick filaments w/o overlapping thin filaments
- H-zone
- M-line
- middle of H-zone; represents filamentous structures that interconnect the thick filaments
- muscle contraction
- width of A-band stays constant; H-zone and I-bands decrease in width
- 3 kinds of muscle fibers
- red, white, and intermediate
- red fibers (small diameter)
- contain an abundant amt of myoglobin and many mitochondria
- predominat in muscles that undergo sustained periods of activity
- red fibers (dark meat)
- white fibers (large diameter)
- less myoglobin and less mitochondria
- contract rapidly and fatigue rapidly
- white fibers (white meat)
- intermediate fibers
- characteristics of red and white fibers
- motor unit
- one motor neuron, axonal branches, and muscle fibers they innervate
- What is the strength of a muscle contraction dependant on?
- how many motor units participate in the contraction
- What innervates muscle fiber?
- motor (effernt) axon
- neuromuscular junction
- site on muscle fiber where axon attaches
- axon terminals
- where axon touches sarcolemna and branches
- motor end plate
- axon terminals and underlying sarcolemna covered by Schwann cells
- synaptic cleft
- small depression of sarcolemna where each axon terminal of a motor end plate sits
- junctional folds
- invaginations of the sarcolemna; contains acetylcholinesterase
-
junctional folds
invaginations of the sarcolemna; contains acetylcholinesterase -
junctional folds
invaginations of the sarcolemna; contains acetylcholinesterase