Tissues Flashcards
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Tissues
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Groups of cells with similar structure and function, vary in content of extracellular matrix
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Extracellular Matrix
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Substance(s) produced by cells of a specific tissue, located on the outside of the cells, may contain protein fibers, salts, water, macromolecules
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Four Primary Tissue Types
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Epithelial (covering), Connective (support), Muscle (movement), Nervous (control)
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Epithelial Tissue
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- Lines the inside and outside of body surfaces, cavities and organs.
- Glands mostly derived from it
- Little/no ECM
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Functions of Epithelium
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- protection
- absorption, secretion, ion transport
- filtration
- forms slippery surfaces
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Characteristics of Epithelia
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- cells fit closely (“cellularity”)
- polarity (“apical” and “basal” surface w/ diff functions)
- junctions on lateral surfaces
- supported by connective tissue
- avascular
- innervated
- regenerate regularly
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Apical Surface
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“top” of cell, part of cell on cavity/lumen side, sometimes has cilia or microvilli
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Basal Surface
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“bottom” of cell, in contact with basement membrane
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Lateral Surface
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“sides” of cell, contain cell junctions (tight junctions, desmosomes, gap junctions)
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Microvilli
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Folded membrane extensions for increasing of surface area in absorptive cells (ex: small intestine)
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Cilia
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cytoskeletal “hairs” used for movement (ex: respiratory epithelia moving mucus out of lungs)
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Tight Junction
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- closely associated areas of two cells whose membranes join together forming a virtually impermeable barrier to fluid
- like “strips of velcro”
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Desmosomes
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- structure specialized for cell-to-cell adhesion
- localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes
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Gap Junction
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directly connects the cytoplasm of two cells, which allows various molecules and ions to pass freely between cells
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Basal Lamina
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non-cellular, avascular layer of fibrils & glycoproteins secreted by epithelia on their basal side to act as a selective filter
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Basement Membrane
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- thin sheet of fibers that underlies the epithelium
- is the fusion of two lamina, the basal lamina and the reticular lamina
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Reticular Lamina
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Connective tissue that makes up part of the basement membrane
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Epithelium Nomenclature
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- “first name” indicates number of cell layers (simple = one, stratified = more than one)
- “last name” describes shape of cells (squamous = wider than tall, cuboidal = cube, columnar = taller than wide)
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Simple Squamous Epithelium
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- one layer of flat cells with disc-like nuclei that bulge out slightly like an egg yolk
- Function: material transport via diffusion/filtration, secretion of lubricating substances
- Location: kidney glomeruli; alveoli, lining of heart, blood and lymph vessels, lining of ventral body cavities
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Endothelium
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- certain kind of simple squamous epithelium
- smooth lining to hollow heart, blood and lymph vessels
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Mesothelium
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- lines peritoneal, pleural and pericardial cavities (parietal)
- covers visceral organs (visceral)
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Simple Cuboidal Epithelium
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- single layer, cube-like cells w/ large spherical central nuclei
- Function: secretion, absorption
- Location: Kidney tubules, ducts and secretory portions of small glands, ovary surface
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Simple Columnar Epithelium
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- Single layer, column-shaped cells with oval nuclei toward the basal end
- may contain goblet cells
- Function: absorption, secretion of mucus, enzymes, etc.
- Location: (non-ciliated) digestive tract, gall bladder (ciliated) small bronchi, uterine tubes, parts of uterus
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Goblet cells
simple columnar epithelial cells that line the intestines, respiratory tract and secrete mucus
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Pseudostratified Columnar Epithelium
- single layer, cells of different heights
- false layered appearance
- may be ciliated
- Function: absorption, secretion, propulsion of mucus by cilia
- Location: (non-ciliated) ducts of large glands, sperm ducts, (ciliated) trachea, upper respiratory tract
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Stratified Epithelia
- 2+ layers
- named according to shape of apical layer cells
- regenerate from below
- mostly for protection
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Stratified Squamous Epithelia
- deeper layers cuboidal or columnar
- Function: protects underlying tissues from abrasion
- Keratinized or non-Keratinized
- Location: (non-keratin) moist linings of esophagus, mouth, vagina (keratin) epidermis
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Keratin
- Keratin is a fibrous structural protein that forms epidermis, hair, nails
- Keratinized Stratified Squamous Epithelia have no nuclei to their apical layer because the cells are dead
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Stratified Cuboidal Epithelium
- usually 2 layers
- Function: protection
- Location: large sweat gland ducts, mammary and salivary gland ducts
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Stratified Columnar Epithelium
- rare
- Function: protection, secretion
- Location: male urethra, large ducts of some glands
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Transitional Epithelium
- cells change shape, allows for stretching
- Basal cells cuboidal/columnar, Apical cells dome-shaped/squamous
- Function: permits distension of bladder, forms barrier for urine
- Location: lines ureters, bladder, part of urethra
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Gland
one or more cells that secrete a particular product
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Endocrine Gland
- lacks ducts
- secretes hormones directed at certain organs ("target" organs)
- use cardiovascular system to transport its products
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Exocrine Gland
- empties through ducts to epithelial surface
- includes sweat/oil glands, mucus glands, salivary glands, liver, pancreas
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Unicellular Exocrine Glands
- located within epithelium
- ex: goblet cell (secrets "mucin" which mixes w/ water to form mucus)
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Multicellular Exocrine Glands
- formed by invagination of epithelium
- made up of a "duct" lined by epithelium and a "secretory unit" lined by secretory epithelium
- 1 name for duct structure, 1 for secretory unit
- ducts are either "simple" or "compound" (unbranched or branched)
- secretory units are "tubular" or "alveolar(/acinar)" or "tubuloalveolar" (some of both)
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Connective Tissue
- most abundant tissue type
- underlies epithelium
- mostly well-vascularized (except tendons, ligaments, cartilage)
- fewer cells
- much more ECM
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Connective Tissue ECM
- Ground Substance is polysaccharides, glycoproteins which hold tissue fluid and varies from soft, gel-like to hard, calcified
- Fibers: "collagen" for strength, "elastic" for stretch, "reticular" for delicacy
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Loose Connective Tissue
- 3 types: Areolar, Adipose, Reticular
- Functions: support and binding of tissues (3 fiber types), holds tissue fluids (ground substance), stores nutrients (adipocytes), defends against infection
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Defense Cells
- Macrophages (phagocytosis)
- Plasma Cells (antibody secretions)
- Mast Cells (inflammation)
- WBCs (neutrophils, eosinophils, lymphocytes)
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Areolar Connective Tissue (Loose)
- most widely distributed (loose)
- contains all 3 fibers
- _Fibroblasts_ are the resident cells, various defense cells too
- Function: wraps and cushions organs, phagocytosis, inflammation, hold tissue fluid
- Location: under epithelia, packages organs, surrounds capillaries
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Adipose Connective Tissue (Loose)
- cells contain large lipid deposits w/ nuclei pushed to edge
- Function: insulation, protection, fuel storage
- Location: under skin, around kidneys/eyes, in abdomen/breasts
- resident cell is known as an _Adipocyte_
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Brown Adipose Tissue
- smaller cells than regular adipose w/ numerous small fat droplets
- vascularized
- generate heat
- have many mitochondria
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Reticular Connective Tissue (Loose)
- delicate fiber network
- Function: internal support of lymphoid organs, supports immune cells, allows for expansion/contraction
- Location: Spleen, Bone Marrow, Lymph Nodes
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Dense Connective Tissue
- ECM is mostly collagen fibers
- resident cells are _Fibroblasts_
- 3 types: Irregular, Regular, Elastic
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Dense Irregular Connective Tissue
- irregularly arranged collagen, some elastic fibers
- Function: withstand multi-directional tension, structural support
- Location: dermis, digestive submucosa, fibrous joint/organ capsules
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Dense Regular Connective Tissue
- parallel collagen fibers, few elastin fibers
- Function: attach muscles and bones to each other, withstand high uni-directional stresses
- Location: tendons, ligaments, aponeuroses
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Dense Elastic Connective Tissue
- high proportion of elastic fibers
- Function: allows recoil following stretching, maintains pulse in arteries, aids passive recoil of lungs after inspiration
- Location: walls of larger arteries, some ligaments of vertebral column, walls of bronchial tubes
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Cartilage
- Firm, flexible tissue
- contains up to 80% water, collagen, ECM
- residents cells are _Chondrocytes_ (_Chondroblasts_ when immature) within _Lacunae_
- avascular and non-innervated
- 3 types: Hyaline, Elastic and Fibrocartilage
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Hyaline Cartilage
- amorphous, firm matrix of imperceptible collagen network
- Function: support, resilient cushioning, resists compressive stress
- Location: embryonic skeleton, ends of long bones, costal (rib) cartilage, nose, trachea, larynx
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Elastic Cartilage
- similar to hyaline w/ more elastic fibers
- Function: maintain shape/structure w/ high flexibility
- Location: support external ear (pinna), epiglottis
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Fibrocartilage
- similar to but less firm than hyaline, mostly thick collagen fibers
- Function: tensile strength, shock absorption
- Location: intervertebral discs, pubic symphysis, discs of knee joint
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Bone
- hard, calcified matrix w/ much collagen
- resident cell is _Osteocyte_ (within lacunae, called _Osteoblasts_ when immature)
- well vascularized
- Function: supports, protects, provides levers for muscle, store calcium, minerals, fat, hematopoiesis
- Location: bones!
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Blood
- blood cells w/ fluid matrix (_plasma_)
- fibers visible during clotting (_fibrin_)
- Function: transport gases, nutrients, wastes, etc.
- Location: within blood vessels
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Membranes
Four types:
1. Cutaneous Membrane - skin (epidermis and dermis)
2. Mucous Membrane - lines hollow organs open to outside (epithelium and areolar lamina propria)
3. Serous Membrane - moist lining of closed cavities (mesothelium, submesothelial CT)
4. Synovial Membrane - fibrous, lines *all* *movable* joint cavities
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Muscle Tissue
- specialized for contraction
- elongated cells forming fibers
- function to produce movement
- 3 types: Skeletal, Smooth, Cardiac
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Skeletal Muscle
- voluntary control
- attached to bone and skin
- cells are long, cylindrical, striated, multinucleate
- nuclei are at edge of cells to make room for myofilaments
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Cardiac Muscle
- only in heart
- involuntary control
- contracts to propel blood through circulatory system
- cells are uninucleate with central nuclei, branched, striated and interdigitate at sites called _intercalated disks_
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Smooth Muscle
- in walls of hollow organs
- constrict and relax involuntarily to move contents
- cells are uninucleate with central nuclei, spindle-shaped, unstriated, closely attached to each other
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Nervous Tissue
- Main cells are _neurons_ (electronically excitable cells), supporting cells are _neuroglial cells_
- Function: transmit electrical signals from sensory receptors and to effectors (muscles and glands)
- Location: brain, spinal cord, nerves
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Dendrites
Branched projections of a neuron that conduct electrochemical signals
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Axon
- AKA 'nerve fiber'
- long, slender projection of neuron that conducts electrical impulses to other neurons, muscles and glands
