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Flashcards in Tissues Deck (63):
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Tissues

Groups of cells with similar structure and function, vary in content of extracellular matrix

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Extracellular Matrix

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

Epithelial (covering), Connective (support), Muscle (movement), Nervous (control)

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Epithelial Tissue

- 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

- protection

- absorption, secretion, ion transport

- filtration

- forms slippery surfaces

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Characteristics of Epithelia

- 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

"top" of cell, part of cell on cavity/lumen side, sometimes has cilia or microvilli

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Basal Surface

"bottom" of cell, in contact with basement membrane

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Lateral Surface

"sides" of cell, contain cell junctions (tight junctions, desmosomes, gap junctions)

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Microvilli

Folded membrane extensions for increasing of surface area in absorptive cells (ex: small intestine)

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Cilia

cytoskeletal "hairs" used for movement (ex: respiratory epithelia moving mucus out of lungs)

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Tight Junction

- 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

- 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

directly connects the cytoplasm of two cells, which allows various molecules and ions to pass freely between cells

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Basal Lamina

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

- 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

Connective tissue that makes up part of the basement membrane

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Epithelium Nomenclature

- "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

- 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

- certain kind of simple squamous epithelium

- smooth lining to hollow heart, blood and lymph vessels

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Mesothelium

- lines peritoneal, pleural and pericardial cavities (parietal)

- covers visceral organs (visceral)

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Simple Cuboidal Epithelium

- 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

- 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