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tissues
groups of cells similar in structure and function
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types of tissues
- epithelial
- connective
- muscular
- nerve
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nervous tissue function and location
- internal communication
- brain
- spinal cord
- nerves
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muscle tissue function and location
- contacts to cause movement
- muscle attached to bones (skeletal)
- muscles of heart (cardiac)
- muscles of walls of hollow organs (smooth)
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epithelial tissue function and location
- forms boundaries between different environments, protects, secretes, absorbs, filters
- skin surface (epidermis)
- lining of GI tract organs and other hollow organs
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connective tissue function and location
- supports, protects, binds other tissues together
- bones
- tendons
- fat and other soft padding tissue
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2 main types of epithelial tissue
- covering and lining epithelia
- glandular epithelia
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characteristics of epithelial tissue
- 1 cells have polarity
- - apical surface - may bear microvilli or cilia
- - basal surface - noncellular basal lamina of glycoprotein and collagen lies adjacent to basal surface
- 2 are composed of closely packed cells - continuous sheets held together by tight junctions and desmosomes
- 3 supported by a connective tissue reticular lamina (under basal lamina)
- 4 avascular but innervated
- 5 high rate of regeneration
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classification of epithelia
- 1 number of layers
- - 1=simple
- - >1=stratified
- 2 type of cell
- - squamous
- - cuboidal
- - columnal
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simple squamous epithelium- description, function, location
- single layer of flattened cells with disc shaped central nuclei and sparse cytoplasm
- allows passage of materials by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae
- kidney glomeruli, air sacs of lungs, lining of heart, blood vessels, lymphatic vessels, lining of ventral body cavity (serosae)
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endothelium
lining of lymphatic vessels, blood vessels, heart
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mesothelium
epithelium of serous membranes in the ventral body cavity
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simple cuboidal epithelium - description, function, location
- single layer of cubelike cells with large spherical central nuclei
- secretion and absorption
- kidney tubules, ducts and secretory portions of sm glands, ovary surface
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simple columnar epithelium - description, function, location
- single layer of tall cells with round to oval nuclei; some bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells)
- absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action
- nonciliated type lines most of the digestive tract, gallbladder and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus
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pseudostratified columnar epithelium - description, function, location
- single layer of cells of differing heights, some not reaching the free suface; nuclei seen at different levels; may contain mucus secreting cells and bear cilia
- secretion, particularly of mucus; propulsion o f mucus by ciliary action
- nonciliated type in male's sperm-carrying ducts and ducts of lg glands; ciliated variety lines the trachea, most of the upper repiratory tract
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stratified squamous epithelium - description, function, location
- thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened; in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers
- protects underlying tissues in aread sujected to abrasion
- nonkeratinized type forms the moist linings of the esophagus, mouth and vagina; keratinized variety forms the epidermis of the skin, a dry membrane
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stratified cuboidal epithelium
- quite rare
- found in some sweat and mammary glands
- typically 2 cell layers thick
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stratified columnar epithelium
- limited distribution in body
- sm amounts in pharynx, male urethra, and lining some glandular ducts
- also occurs at transition areas between two other types of epithelia
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transitional epithelium - description, function, location
- resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamouslike, depending on degree of organ stretch
- stretches readily and permits distension of urinary organ by contained urine
- lines the ureters, urinary bladder, and part of the urethra
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gland
one or more cells that makes and secretes an aqueous fluid
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gland classification
- site of product release
- - endocrine
- - exocrine
- relative number of cells forming the gland
- - unicellular (goblet cells)
- - multicellular
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endocrine glands
- ductless
- secrete hormones that travel through lymph or blood to target organs
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exocrine glands
- more numerous than endocrine glands
- secrete products into ducts
- secretions released onto body surfaces (skin) or into body cavities
- mucous, sweat, oil, salivary
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unicellular exocrine glands
- goblet cell
- - microvilli
- - secretory vesicles
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multicellular exocrine glands
composed of a duct and a secretory unit
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classification of multicellular exocrine glands
- 1 duct type
- - simple
- - compound
- 2 structure of secretory unit
- - tubular
- - alveolar
- - tubuloalveolar
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simple tubular gland
- duct doesn't branch
- intestinal glands
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simple branched tubular
- has "nubs"
- stomach (gastric) glands
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compound tubular
- definite branching
- duodenal glands of small intestine
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simple alveolar
- single "trunk"
- alveolar = berry like
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simple branched alveolar
- has "nubs"
- sebaceous (oil) glands
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compound alveolar
- definite branching
- mammary glands
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compound tubuloalveolar
- some are tubular some alveolar
- definite branching
- salivary glands
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modes of secretion
- merocrine - secretion by exocytosis (pancreas, sweat, salivary)
- holocrine - secretion by rupture of gland cells - cell blows up (sebaceous glands)
- apocrine - secretion by blowing its top, reforms new top
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connective tissue
most abundant and widely distributed tissue type
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4 classes of connective tissue
- connective tissue proper
- cartilage
- bone tissue
- blood
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major functions of connective tissue
- binding and support
- protection
- insulation
- transportation (blood)
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characteristics of connective tissue
- mesenchyme is their common tissue of origin
- varying degrees of vascularity
- cells separated by nonliving extracellular matrix (ground substance and fibers)
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structural elements of connective tissue
- ground substance
- fibers
- cells
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ground substance of connective tissue
- medium through which solutes diffuse between blood capillaries and cells
- components
- - interstitial fluid
- - adhesion proteins
- - proteoglycans - protein core + lg polysaccharides (chondroitin sulfate and hyaluronic acid); trap water in varying amounts, affecting the viscosity of the ground substance
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3 types of fibers in connective tissue
- 1 collagen (white fibers)
- - strongest and most abundant type
- - provides high tensile strength
- 2 elastic
- - networks of long, thin, elastin fibers that allow for stretch
- 3 reticular
- - short, fine, highly branched collagenous fibers
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cells of connective tissue
- mitotically active and secretory cells - blasts
- mature cells - cytes
- - fibrocells in connective tissue proper
- - chondroblasts and chondrocytes in cartilage
- - osteoblasts and osteocytes in bone
- - hematopoietic stem cells in bone marrow
- - fat cells, white blood cells, mast cells, and macrophages
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mesenchyme
- embryonic connective tissue
- - gives rise to all other connective tissues
- - gel-like ground substance with fibers and star-shaped mesenchymal cells
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connective tissue proper: loose connective tissue, areolar - description, function, location
- gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some white blood cells
- wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid
- widely distributed under epithelia of body (forms lamina propria of mucous membranes); packages organs; surrounds capillaries
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connective tissue proper: loose connective tissue, adipose
- matrix as in areolar, but very sparse; slosely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet
- provides reserve food fuel; insulates against heat loss; supports and protects organs
- under skin in the hypodermis; around kidneys and eyeballs; within abdomen; in breasts
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connective tissue proper: loose connective tissue, reticular - description, function, location
- network of reticular fibers in a typical loose ground substance; reticular cells lie on the network
- fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages
- lymphoid organs (lymph nodes, bone marrow, and spleen)
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connective tissue proper: dense connective tissue, dense regular - description, function, location
- primarily parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast
- attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction
- tendons, most ligaments, aponeuroses
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connective tissue proper: dense connective tissue, dense irregular - description, function, location
- primarily irregularly arranged collagen fibers; some elastic fibers; major cell type is the fibroblast
- able to withstand tension exerted in many directions; provides structural strength
- fibrous capsules of organs and of joints; dermis of the skin; submucosa of digestive tract
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connective tissue proper: dense connective tissue, elastic - description, function, location
- dense regular connective tissue containing a high proportion of elastic fibers
- allows recoil of tissue following stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following inspiration
- walls of large arteries; within certain ligaments associated with the vertebral column; within the walls of the bronchial tubes
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cartilage: hyaline - description, function, location
- amorphous but firm matrix; collagen fibers form and imperceptible network; chondroblasts produce the matrix and when mature (chondrocytes) lie in lacunae
- supports and reinforces; has resilient cushioning properties; resists compressive stress
- forms most of the embryonic skeleton; covers the ends of long bones in joint cavities; forms costal cartilages of the ribs; cartilages of the nose, trachea and larynx
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cartilage: elastic - description, function, location
- similar to hyaline cartilage, but more elastic fibers in matrix
- maintains the shape of a structure while allowing great flexibility
- supports the external ear (pinna); epiglottis
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cartilage: fibrocartilage - description, function, location
- matrix similar to but less firm than that in hyaline cartilage; thick collagen fibers predominate
- tensile strength with the ability to absorb compressive shock
- intervertebral discs; pubic symphysis; discs of knee joint
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other connective tissues: bone (osseous tissue) - description, function, location
- hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae. very well vascularized
- bone supports and protects (by enclosing); provides levers for the muscles to act on; stores calcium and other minerals and fat; marrow inside bones is the site for blood cell formation (hematopoiesis)
- bones
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other connective tissues: blood - description, function, location
- red and white blood cells in a fluid matrix (plasma)
- transport of respiratory gases, nutrients, waste and other substances
- contained within blood vessels
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2 major cell types of nervous tissue
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nervous tissue - description, function, location
- neurons are branching cells; cell processes that may be quite long extend from the nucleus-containing cell body; also contributing to nervous tissue are nonirritable supporting cells
- transmit electrical signals from sensory receptors and to effectors (muscles and glands) which control their activity
- brain, spinal cord and nerves
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muscle tissues
- highly cellular
- well vascularized
- responsible for most types of body movement
- cells possess myofilaments
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skeletal muscle - description, function, location
- long, cylindrical, multinucleate cells; obvious striations
- voluntary movement; locomotion; manipulation of the environment; facial expression; voluntary control
- in skeletal muscles attached to bones or occasionally to skin
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cardiac muscle - description, function, location
- branching, striated, generally uninucleate cells that interdigitate at speciallized junctions (intercalated discs)
- as it contracts, it propels blood into the circulation; involuntary control
- the walls of the heart
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smooth muscle - description, function, location
- spindle-shaped cells with central nuclei; no striations; cells arranged closely to form sheets
- propels substances or objects (foodstuffs, urine, a baby) along internal passageways; involuntary control
- mostly in the walls of hollow organs
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3 covering and lining membranes
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cutaneous membrane - description, location
- keratinized stratified squamous epithelium attached to a thick layer of dense irregular connective tissue(dermis)
- skin
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mucous membrane
- moist membranes bathed by secretions or in the case of urinary mucosa, urine
- line the body cavities that open to the exterior
- - hollow organs of the digestive, respiratory and urogenital tracts
- most contain either stratified squamous or simple columnar epithelia
- epithelial layer is underlain by a layer of loose connective tissue called the lamina propria
- some have a deeper layer of smooth muscle cells
- absorption and secretion
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serous membranes
- consists of simple squamous epithelium (mesothelium) resting on a thin layer of loose connective (areolar) tissue
- mesothelial cells add hyaluronic acid to the fluid that filters fromt he capillaries in the associated connective tissue resulting in serous fluid
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steps of tissue repair
- 1 inflammation
- - severed blood vessels bleed and inflammatory chemicals are released
- - local blood vessels become more permeable, allowing white blood cells, fluid, clotting proteins and other plasma proteins to seep into the injured area
- - clotting occurs; surface dries and forms a scab
- 2 organization
- - the clot is replaced by granulation tissue, which restores the vascular supply
- - fibroblasts produce collagen fibers that bridge the gap
- - macrophages phagocytize cell debris
- - surface epithelial cells multiply and migrate over the granulation tissue
- 3 regeneration
- - the fibrosed area matures and contracts; the epithelium thickens
- - a fully regenerated epithelium with a underlying area of scar tissue results
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regenerative capacity of different tissues
- very good regeneration - epithelial tissues, bone, areolar connective tissue, dense irregular connective tissue, and blood-forming tissue
- moderate regen - smooth muscle and dense regular connective tissue
- weak regen - skeletal muscle and cartilage
- no functional regen - cardiac muscle and nervous tissue in the brain and spinal cord
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3 primary germ layers
- ectoderm - produces nervous tissue
- mesoderm- produces muscle and connective tissues
- endoderm - along with ecto and meso produce epithelium
- these form all 4 of the tissues found in the body
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proliferation of body cells during development
- nerve cells stop dividing ( or mostly) during fetal period
- after birth the cells of most other tissues continue to divide until adult body size
- tissues that regenerate throughout life
- - epithelia
- - blood-forming tissues
- liver cells regenerate by division of adult cells
- epidermis and cells lining intestine have abundant stem cells
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affects of aging on tissue development
- epithelia thin
- tissue repair is less efficient
- bone, muscle and nervous tissues begin to atrophy
- decreased circulatory efficiency leads to reduced delivery of nutrients to tissues
- DNA mutations increase
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cancer
disorganized cell growth
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neoplasm
abnormal mass of proliferating cells
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benign
- cells remain compacted
- slow growth
- often encapsulated
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malignant
- nonencapsulated
- grow relentlessly
- cells invade their surroundings - metastasis
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proto-oncogenes
- code for proteins that are essential for cell division, growth, and cellular adhesion
- dmg (from carcinogens) can turn them into oncogenes
- oncogenes may "switch on" dormant genes that allow cells to become invasive and metastasize
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tumor suppressor genes
- suppress cancer by inactivating carcinogens, aiding DNA repair, or enhancing the immune system's counterattack
- loss or malfunction of just 2 can lead to cancer
- one prompts most cells to make proteins that stop cell division in stressed cells by promoting apoptosis or cell cycle arrest
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