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Tissues
- cells of a similar type and function clustered into layers or sheets
- cells are like individuals - can complete individual job, but need to work together in tissues
- result of differentiation and specialization
- must cooperate with other cells for an organism to function
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Epithelial tissue
- divides readily in adults
- eg mucus mebranes, cornea, skin
- develops into carcinomas (cancer)
- composed of sheets or layers
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Epithelial tissue functions
- protects, lines and covers
- filters - kidneys
- absorbs
- senses
- secretes
- excretes
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Glandular epithelium
- responsible for excretion and secretion
- two types:
- - cellular - goblet cells - eg pseudostratified ciliated epithelium - individual drops of mucus
- - organ - pancreas
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Excretions
- leave the body
- "ex" like exit
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Secretions
- stay within the body
- "sec" like secret
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Epithelial tissue characteristics
- cells are tightly packed (shoulder to shoulder) to form sheets or layers
- polar - recognizable top and bottom
- adhere via junctional complexes
- avascular - no blood vessels - eg paper cuts that don't bleed
- innervated - lots of nerve endings
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Cellular attachments in epithelial cells
- three types:
- - tight junction
- - gap junction
- - desmosome
- space between cells contains a matrix that allows for nutrients to reach cell
- in any given type of epithelial tissues there can be more than one junction type (or all 3)
- - cardiac - desmosomes and gap junction
- determined genetically
- as you get older, ability to make junctions decreases, so old skin tears easily
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Tight junctions
- occlusive
- no leakage
- seen in:
- - bladder
- - GI tract
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Desmosomes
- needs 2 cells to link
- plaque or thickening
- extremely strong - like a weld
- mechanical - interlocking filaments
- filaments extend into the cell
- skin, heart, uterus - don't want cells to separate
- hemidesmosomes - basement membrane
- epithelial cell sends fibers into connective tissue & connects to fibers in there
- only one cytoplasmic plaque that acts like a washer
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Gap junction
- transmembrane tubular proteins connect cytoplasm of one cell with the cytoplasm of the next cell
- proteins are called connexons
- intestinal, cardiac and smooth muscle
- virus and intraplasmic bacteria love these
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Basement membrane
- non-living mesh of fibers that cements the epithelial cell to the underlying connective tissue (the collagen in it)
- hemidesmosomes
- manufactured by the epithelial cells
- nutrients and waste diffuse across the basement membrane out of/in to connective tissue where blood vessels takes away/brings
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Apical surface
- apical - from apex
- free border
- opens to space - lumen
- specialization
- - microvilli
- - cilia
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Microvilli
- fingerlike projections increase the surface area
- brush border
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Cilia
- hairlike
- enables movement of material along cell surfaces
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Classification of epithelial tissue
- number of cell layers:
- - one layer - simple
- - greater than one layer:
- -- stratified
- -- psuedostratified
- shape of cells:
- - squamous - flat
- - cuboidal - square
- - columnar - rectangular
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Simple squamous epithelium
- thin and delicate - so gases move right through
- line surfaces that exchange gas or liquid by diffusion/osmosis
- line thorax and abdomen
- - mesothelium
- -- mesothelioma - tumors of mesothelium
- line blood vessels
- - endothelium
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Simple cuboidal epithelium
- single layer of cuboidal cells
- secretory glands
- - endocrine
- -- thyroid
- - exocrine
- -- salivary
- -- pancreas
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Apical surface
surface toward lumen
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Basal surface
surface toward connective tissue
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Simple columnar epithelium
- elongated, closely packed cells
- nuclei located at base of cell
- associated with GI tract
- - absorptive cells
- - goblet cells are present
- excretory ducts - sometimes columnar in duct; cuboidal in secretory portion
- respiratory tract
- - ciliated
- e.g. hair - keratin produced in epithelial cells in scalp
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Stratified squamous epithelium
- multiple layers of flat cells
- in areas of mechanical and/or chemical stress
- - mouth
- - vagina
- - rectum
- keratinized (on exterior) or not (on interior surface)
- cuboidal to squamous - basement is cuboidal, flatten as they move up
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Stratified cuboidal epithelium
- "boutique tissue"
- 2 layers of cells (both cuboidal)
- lines large ducts of exocrine glands
- only 3 places in the body:
- - mammary - milk
- - sweat
- - salivary
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Pseudo stratified columnar epithelium
- pseudo - false
- cells in a single layer
- - all are attached to basement membrane
- nuclei are staggered through compression
- - like a crowd that contains adults and children
- not all cells apical surfaces reach lumen
- ciliated
- in respiratory tree
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Transitional epithelium
- stretchy
- cells are rounded and dome like when relaxed, flattened and squamous when distended
- in bladder and other urinary structures
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Gland
a single cell or group of cells that have the ability to manufacture and discharge a secretion
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Secretion
specialized protein molecules produced by the RER (rough ER) and packaged by the Golgi apparatus
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Glandular epithelium
- secretions are stored as granules within the cell
- eg histamine granules you can see in eosinophils with a microscope
- eg eosinophils secrete granules that let the rest of immune system know its under attack & needs to start working
- develop as invaginations of epithelium in the embryo
- the invaginations form ducts and tubules
- as the embryo develops, some of the ducts are lost and the gland becomes embedded in the deeper tissue
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Classification of glands
- presence or absence of ducts
- number of cells composing gland
- shape of the secreting ducts
- complexity of the glandular structure
- type of secretion
- manner of secretion
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Endocrine glands
- endo - inside
- lack ducts
- produce hormones
- secrete directly into the blood
- part of a complex system
- the slow and steady part of the nervous system (but not really)
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Pineal gland
- makes melatonin
- helps adjust to seasons
- communicates with pituitary
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Pituitary gland
inhibits/stimulates rest of endocrine system
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Thyroid gland
tells you to start laying down fat in winter
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Exocrine glands
- possesses ducts
- - classified by duct arrangement
- discharge secretions locally
- sweat, saliva, mucus, anal gland secretions are produced by exocrine glands
- pancreatic duct goes to small intestines to help digest food
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Adenoma
benign tumor of gland
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Duct arrangements
- simple, branched or compound
- tubular, coiled tubular or alveolar (grapelike)
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Unicellular exocrine glands
- goblet cells
- modified columnar epithelial cell
- secrete
- - mucin - proteoglycans & glycoprotein that becomes mucus when contacts water
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Proteoglycans
molecule that contains protein & sugar - more sugar than protein
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Glycoprotein
molecule that contains protein & sugar - more protein than sugar
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Multicellular exocrine glands
- composed of 2 components:
- - secretory unit
- - duct
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Secretory unit
- eg hot water heater makes hot water
- may be surrounded by myoepithelial cells to assist discharge of secretions
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Myoepithelial cells
make actin & myosin fibers to allow contraction of glands
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Duct
- eg pipes that carry hot water
- unbranched - simple
- branched - compound
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Classification of secretory portion of exocrine glands
- tubular - channel of even width
- acinar (alveolar) - rounded sac
- tubulaveolar (acinar) - qualities of both tubular and acinar
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Methods of exocrine secretion
- merocrine
- apocrine
- holocrine
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Merocrine
- secretion is released - secretory vesicle meshes with cell membrane
- cell remains intact
- sweat and saliva
- - percieve as H2O
- - no lipids, just protein
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Apocrine
- apex of cell is lost during secretion - pinched off portion of cell contains secretion
- mammary and sweat (really sticky sweat)
- plasmalemma = fat in milk
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Holocrine
- entire cell is destroyed upon release of secretion
- sebaceous glands
- - produce sebum (oil on skin), eg lanolin
- - sebaceous adenomas filled with cottage cheese like substance
- - eg ear wax
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Types of exocrine secretion
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Serous exocrine secretion
- watery
- enzyme rich
- generally merocrine solutions
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Mucus exocrine secretions
- thick
- composed of glycoproteins
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Mixed exocrine secretions
- eg tears
- contain both a mucus and serous component
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Connective tissue
- supports other tissues
- divides readily in adults
- develops into sarcomas
- - vaccine related sarcoma come from fibroblasts
- most abdundant tissue by weight
- most is derived from the mesoderm
- mainly composed of nonliving, extracellular matrix
- think of it as glue that holds the body together
- highly vascular
- doesn't mend itself like new if severed (like severed thread or rope)
- - never as strong as before
- - make mesh patch (synthetic) - sew on both sides of break - still not as strong
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Components of Connective tissue
- extracellular fibers
- ground substance
- - ground as in background
- - different kinds
- - outside cells
- cells
- - fibroblast - young; makes fibers
- - mast cell macrophages - all connective tissue
- fibers and ground substance create matrix
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Connective tissue morphology
- connective tissues vary in proportion of cells, fibers, matrix giving rise to a wide variety of morphologies
- - blood - ground subs=plasma, fiber=dissolved fibrin, cells= RBC & WBC
- - tendon - mostly collagen, not many cells, not much matrix
- - fat - adipose cells, fibers in between; cellulite is fibrous
- - bone (calcified) - cellular, calcified matrix
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Connective tissue functions
- provide metabolic and structural connections
- - tendon holds muscle to bone
- protection
- - bones protect soft organs
- - fat - soft tissue
- energy reserve - fat
- transport medium
- - blood - transport for all substances in body
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Ground substance
- amorphous - blob-like
- homogenous
- - uniform throughout
- - liquid, semi-solid (gel) or calcified
- - glycoaminoglycans (GAGS)
- -- hyalauronic acid
- -- helps orient fibers correctly
- -- protien has nitrogen
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Fibers
- collagenous
- retivcular
- elastic
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Collagenous fibers
- most common
- strong and thick
- fibrils and microfibrils
- "white fibers"
- density and orientation determines function
- building block of all fibrous tissues
- think of collagen as a piece of monofilament (fibril)
- - put together, makes fiber
- - put more together, yarn
- - put more together, rope
- - within body, can find all sizes
- anabolic steroids damage collagen
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Reticular fibers
- thin, delicate arrangements of collagen molecules
- under epithelium
- support highly cellular organs
- - hold up nephrons in kidney
- - blood vessels follow reticular fibers
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Elastic fibers
- elastin
- - diff protein than collagen
- - like diff between thread and rubber band
- lack tensile strength
- - if you pull hard enough, it breaks
- eg earlobes
- eg horses - ligamentum nuchae
- - from skull to base of spine
- - holds head up
- - must use muscle to put head down
- eg arteries around the heart has these to allow blood flow
- - hardening of the arteries is loss of elasticity
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Connective tissue cells
- fixed
- transient (wandering)
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Fixed cells
- fibroblast
- fat (adipocytes)
- reticular
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Fibroblast (fixed cells)
- secrete fibers and ground substance
- named by the tissue they are found in:
- - chondro - make cartilage
- - osteo - make bone
- blasts - actively producing
- cytes - mature cells that have stopped producing
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Reticular Cells (fixed cells)
- star shaped
- reticular fibers
- immune function
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Transient (wandering) cells
- move in and out of connective tissue
- leukocytes - neutrophils
- - diapedesis
- -- literally - walking across
- -- move out of connective tissue along reticular fibers using myosin & actin
- mast cells
- - histamines & heparin
- - inflammatory response
- macrophages
- - massive
- - fixed or transient
- - named based on tissue location (leftover from when we didn't know as much):
- -- Kupffer - liver
- -- microglial - brain
- -- histiocyte
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Categories of Connective Tissue
- connective tissue proper
- specialized connective tissue
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Connective tissue proper
- categorized by how many fibers & their pattern
- dense connective tissue - numerous fibers
- loose connective tissue - fewer fibers
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Dense connective tissue
- dense regular - collagen
- dense irregular - collagen
- elastic - elastin
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Dense regular connective tissue
- collagen fibers are tightly packed and aligned in a parallel pattern
- relatively avascular
- little ground substance, so no slime factor
- tendons
- ligaments
- fascia
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Dense irregular connective tissue
- collagen fibers are interwoven in thick bundles
- dermis
- organ capsules
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Elastic connective tissue
- primary fibers are elastin, not collagen
- disks
- arteries
- bladder
- ligamentum nuchae
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Areolar (loose connective tissue)
- most common
- covers everything
- small open spaces
- cells - fibroblasts
- ground substance - hyaluronic acid (when peel skin off chicken, this is slimy, gel-like goo)
- fibers - all 3 types: reticular, collagen, elastin
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Adipose tissue (loose connective tissue)
- Fat
- little ground substance, few fibers
- adipocytes - cells
- - brown adipose tissue
- - white adipose tissue
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Brown adipose tissue
- cell respiration - heat, not ATP
- hibernation and neonates - cannot thermoregulate
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Hibernation
- torporous state
- when cold, shiver, brown fat produces heat, so don't need to wake up to exercise to get warm
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White adipose tissue
- highly vascular
- energy store
- protection
- insulation - keeps you warm
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Reticular Connective tissue (loose connective tissue)
- thin reticular fibers
- fibroblasts
- stroma
- - structure formed by connective tissue that other cells adhere to
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Specialized connective tissue
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Cartilage
- aka gristle
- more rigid than connective tissue proper
- avascular - perichondrium
- aneuronal - no nerve endings
- ends of long bone, nose, ear, vocal cords
- cells - chondroblasts (/cytes)
- - lacunae
- matrix:
- - hyaluronic acid
- - chondroitin sulfate
- - chondronectin
- fibers - collagen
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Types of cartilage
- hyaline
- elastic
- fibrocartilage
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Hyaline cartilage
- most common
- glass like - can't identify fibers in matrix
- covers ends of bones
- if damaged, is replaced by fibrocartialage
- supports trachea
- perichondrium
- - provides nutritional support
- - vascular
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Fibrocartilage
- fibers are coarser than hyaline cartilage
- junction of hyaline cartilage and dense regular connective tissue
- no perichondrium
- - menisci - in knee
- - disks - between vertebrae
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Elastic cartilage
- many elastic fibers
- epiglottis
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Bone
- highly vascular
- osseous connective tissue
- organic - collagen
- inorganic - calcium salts
- osteocytes - mature
- osteoclasts
- - bone eaters
- - when you need calcium and don't get enough in diet
- periosteum
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Blood
- cells
- - erythrocytes
- - leukocytes
- - platelets (pieces of thrombocytes)
- matrix
- - plasma - protein rich - particularly albumin
- fibers
- - fibrinogen - fibrin - transform under appropriate circumstances
- aspirin stops platelets from getting sticky
- - when platelets slow down they get sticky
- - blocked arteries can slow them down enough to make them sticky
- FIP - fluid pulled out full of fibrin
- hemorrhage - put pressure on for 5 minutes to allow form to clot
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Membranes
- intermediate step between tissues and organs
- connective tissue & epithelium working together
- - line body cavities - pleura & peritoneum
- - separate organs
- - cover surfaces
- -- frequently bathed in fluid
- --- urine - bladder
- --- mucus - lining of respiratory tree
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Types of membranes
- named for what they produce
- mucous
- serous - watery, eg pleural
- cutaneous - produce sebum, eg skin
- synovial - lines joints that move
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Mucous membranes
- mucosae
- line organs that connect to the outside
- - bladder, intestines, respiratory tree, reproductive tract
- epithelial layer - stratified squamous or simple columnar (may be pseudo stratified)
- connective tissue - lamina propria - literally proper layer
- produce mucus
- animals can get sinus headaches, esp cats - when scruff can compress sinuses & hurt
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Serous membranes
- serosae
- cover organs and body cavities that don't open to exterior
- - parietal - attached to body wall
- - visceral - attached to organ
- simple squamous epithelium
- attached by loose areolar connective tissue
- produce transudate - thin & watery
- named for locaton:
- - pleural fluid
- - peritoneal fluid
- disease creates changes in membrane and fluid
- exudate
- - cells & protein added to transudate
- - check protein with refractometer
- effusion
- - ascites
- - leakage from membrane
- abdomino/thoracocentesis
- - ques is it transudate (tend to be acellular) or exudate
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Mesenteries
- special serous membrane
- thin material (web like) between blood vessels
- - keeps them fanned out
- - can twist & intestine will die
- stomach mesentery called omentum
- mesentery is continuous with peritoneum
- peritoneal space has organs covered with visceral peritoneum
- blood vessels originate from aorta along spine
- cranial & caudal mesenteric arteries branch to different pieces of intestine
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Cutaneous membrane
- integument - skin
- keratinized stratified squamous epithelium (epidermis - on top of dermis)
- dermis - connective tissue that supports epidermis
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Synovial membranes
- lines the cavities of freely moveable joints
- no epithelium - this makes it unique
- only has connective tissue
- loose connective tissue covered bu adipose tissue and a layer of collagen and fibroblasts
- swollen joint has too much synovial fluid
- - highly proteinaceous, no cells normally
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Muscle tissue
- prefix = myo
- composed of cells called fibers (gross description, not same as fibrous connective tissue)
- cells contain filaments (little threads) composed of actin & myosin
- 3 types:
- - skeletal
- - smooth
- - cardiac
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Skeletal muscle
- long, large, multinucleate cells
- voluntary - controlled through concious thought
- striated
- associated with nerves
- - paresis - weakening of muscle
- - paralysis - loss of function
- shortens when it contracts
- every muscle fiber has an axon terminal to allow range of motion from small to large
- - touching someone vs punching them
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Paresis
- weakening of muscle
- hard to assess in animals
- - sled dogs that can't pull as much as they used to
- - draft horses can't do as much work as they used to
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Smooth muscle
- small, spindle shaped cells
- no striations
- walls of hollow organs and blood vessels
- nonstraiated, involuntary muscle
- still have actin & myosin
- scrunches when contracts
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Cardiac muscle
- found only in the heart
- myocardium
- involuntarty, striated
- branched
- intercalated disks (junctures)
- think of it as joint in water pipe - bolted together, but hollow so water can flow
- cells all communicate so heart beats together
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Neural tissue
- neurons & neuroglial cells
- transmit & recieve electrical impulses
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Neurons
- perikaryon (cell body)
- dendrites
- axons
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Neuroglial cells
- connective tissue
- most numerous cells in the neural tissue
- highly specialized
- - astrocytes - blood-brain barrier
- - oligodendrocytes - myelin sheath
- - microglia - phagocytosis - basically macrophages
- - ependymal - CSF (cerebrospinal fluid)
- small cells around large motor neurons
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