Tissues Flashcards

1
Q

Define Tissue

A

Tissue: A group of cells performing similar functions

-vary in structure, function & content of their extracellular matrix (can contain protein fibres, salts, H20 & dissolved macromolcules)

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2
Q

4 Types of Tissues

A
  1. Epithelial Tissue
  2. Connective Tissue
  3. Muscle Tissue
  4. Nervous Tissue
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3
Q

Epithelial Tissue - 6 General characteristics

A
  • Lines every body surface and all body cavities (organs lined on the outside and inside & majority of glands are derived from epithelial tissue)
    1. Cellularity: composed almost entirely of cells - little extracellular matrix w/ cells bound together w/ intercellular junctions
    2. Polarity - have apical suface & basal surface (i.e. lots of channels - one side of cell exposed, other not)
    3. Attachment - Basal surface attached to thin basement membrane
    4. Avascularity - lack blood vessels (nutrients via diffusion from underlying tissue)
    5. Innervation - Richly innverated to detect changes in enviro
    6. Regeneration - apical surface in constant contact w/ enviro (freq. damaged/die)
    • replaced quickly
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4
Q

4 Functions of Epithelial Tissue

A
  1. Physical Protection: From dehydration & abrasion (phys. chem. bio.)
  2. Selective Permeability: needs to absorb certain things from enviro.
  3. Secretions: exocrine cells produce secretions such as sweat & oil (may be scattered amount other cell types in epithelium or may form a gland)
  4. Sensations: possess nerve endings that can detect light, taste, sound, smell & hearing
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5
Q

Basement Membrane

A
  • is a specialised structure of epithelium
  • found between epithelium & underlying connective tissue
  • provides physical support and anchoring of epithelial tissue
  • acts as barrier to regulate passage of large molecules between epithelium & underlying connective tissue

*is actually composed of 3 layers that all strengthen attachment & form a selective barrier

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6
Q

Intercellular Junctions - 4 types

A
*Epithelial cells strongly bound to each other by sharing membrane specialisations
4 types;
1. Tight junctions
2. Adhering Junctions
3. Desmosomes (or hemidesmosomes)
4. Gap junctions
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7
Q

Tight Junctions

A
  • Encircle cells near apical surface
  • Prevents molecules from travelling between - must go through epithelial cells to reach basal membrane (are therefore gatekeepers)
  • provides structure & support at apical surface.

-in small intestine, prevent digestive enzymes that degrade molecules from moving between epithelial & connective tissue

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8
Q

Adhering Junctions

A
  • Formed completely around the cell deep to tight junctions
  • microfilaments act like a purse string to stabilise the apical surface (is a strengthening belt of the cell)
  • provide a small space between neighbouring cells in direction of basal surface = passage between cells for materials that have already passed through epithelial cell
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9
Q

Desmosomes

A
  • Doesn’t totally encircle cell
  • Like a button or snap between adjacent cells - joins cells together
  • At places of mechanical stress between cells
  • Have thickened protein plaque on each of apposed cell membranes w/ fine network of proteins spanning intercellular space
  • On cytoplasmic side, intermediate filaments attach to plaques & provide suppot and stability
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10
Q

Gap Junctions

A
  • Fluid filled channels that directly connect the cytoplasms of apposed cells sharing these structures
  • allow adjacent cells to communicate w/ each other by flow of ions & other small molecular messengers (i.e. glucose, a.a.)

i.e. muscle cells for contraction along muscle - might need communication along.

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11
Q

Epithelia Classification

A

*classified based on shape of cells (at most superficial surface) & no. of cell layers

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12
Q

Epithelial Cell Shapes (3)

A
  1. Squamous: flattened, wide, irregular w/ large nucleus (like a fried egg)
  2. Cuboidal: about same size on all sides - nucleus centrally located (but do NOT have edges)
  3. Columnar - taller than they are wide (nucleus is oval & located in basal region)
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13
Q

Epithelium Cell Layers (3)

A
  1. Simple Epithelium: single layer of cells w/ all cells having apical surface & attached to basement membrane (apical often covered by thin layer of fluid or mucus for protection)
    • found where stress minimal & absorption, filtration or secretion is primary function
  2. Stratified epithelium - 2+ layers (not all have apical surface or attach to basal membrane)
    • areas subject to abrasive or mechanical stresses
  3. Pseudostratified epithelium - single layer - not all cells reach apical surface
    • Nuclei give appearance of multilayered, stratified epithelium (those that do reach often have cilia to help move fluid along)
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14
Q

Types of Epithelium & Location (Simple)

A
  • Simple Squamous Epithelium: single layer of flat cells (allows rapid diffusion: lungs, blood vessels & membranes that cover body cavities)
    - Endothelium (lines lumen of blood & lymphatic vessels & heart & its chambers
    - Mesothelium (serous membrane that lines internal walls of pericardial, pleural & peritoneal cavities)
  • Simple Cuboidal: forms ducts of exocrine glands (gen. involved in absorption & secretion)
  • Simple columnar: I.e. small intestine (involved in absorption & secretion
  • Simple Columnar Ciliated - Possess cilia on apical surface such as in respiratory and reproductive systems
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15
Q

Types of Epithelium & Location/function (Stratified)

A
  • Stratified Squamous Cells - in areas w/ lots of stress as provide protection for underlying tissue
    • either exists as nonkeratinized (remains alive w/ mucous or saliva) or keratin (apical = cells that are deal & lack a nucleus - such as outer layer of skin)
  • Stratified Cuboidal Epithelium: Generally found in glandular tissue (i.e. sweat or semen), although function is mainly protective (serves to strengthen wall of gland ducts)
  • Stratified Columnar - quite rare to fine (e.g. male urethra)
  • Psuedostratified Columnar - not really stratified as all cells in contact w/ basement membrane - looks stratified as not all cells reach apical surface.
    • often covered w/ cilia, generally involved in protection
    • found in respiratory tract, naval cavity
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16
Q

Transitional Epithelium - what it is, where found & distinct Feature

A
  • Found in the lining of the urinary bladder
  • Changes shape between squamous and cuboidal depending on whether bladder if full or empty (walls stretched or contracted)
    - when stretched: resemble squamous cells
    - When relaxed: polyhedral (many sided)
  • Distinct feature: presence of few binucleated cells
  • Cells aren’t uniform - are bunched up
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17
Q

Glands - Function

-2 Categories

Definition of Duct

A
  • Perform secretory function
    • produce mucin, hormones, enzymes & waste products

2 categories;

  1. Exocrine glands: possess ducts that cells secrete products into - almost all derived from epithelial tissue
    • i.e. milk, sweat, mucous, saliva glands
  2. Endocrine Glands: do not possess ducts - cells secrete products into interstitial fluid or bloodstream - derived from multiple tissue
    • i.e. hormones

Duct: epithelium lined tube through which secretions of glands are discharged to epithelial surface

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18
Q

Connective Tissue - Overview

A
  • Is most diverse, abundant, widely distributed and structurally varied of all tissue types
  • serves to connect structures together
  • Is the glue AND filler of the body
    • designed to support, protect & bind organs`

e.g. tendons, ligaments, body fat, bones & cartilage

19
Q

3 structural components of Connective Tissue

A
  1. Cells: differ between types of connective tissue (CT)
    • i.e. fibroblasts produce fibres, adipocytes = fat, chondrocytes = cartilage
  2. Protein Fibres: elastic fibres (flexibility), collagen (strength), reticular fibres (interwoven framework)
  3. Ground Substance: mix of proteins & carbs w/ variable amounts of salts and H2O
  • Protein fibers and ground substance comprise extracellular matrix - produced by CT cells
  • Most CT = mainly extracellular matrix w/ small portion of cells (relative to epithelial)).

*Different connective tissues vary in these components

20
Q

Protein fibres in CT (3)

A
  • Elastic fibres
  • collagen fibres
  • Reticular fibres
21
Q

6 Functions of connective tissues

A

PBS-STI

  1. Physical protection - fat can protect kidneys, axial cavity can protect brain, heart, lungs
  2. Binding of structures - e.g. ligaments, tendons
  3. Support and structural frameworks - bones allow soft tissue to connect
  4. Storage - fat for energy, Bone for Ca & P
  5. Transport - blood transports nutrients
  6. Immune Protection - WBC can ward off infection/disease
    • extracellular matrix is viscous material that interferes w/ movement and spread of disease-causing organisms
22
Q

3 Broad classifications of Connective Tissues

A
  1. CT Proper
  2. Supporting CT
  3. Fluid CT
23
Q

Connective Tissue Proper - 2 Categories (3 types within each category)

A
  1. Loose CT: fewer protein fibres & more ground subs.
    - serves as body’s packing material - found in spaces around organs
    • 3 types: areolar, adipose, reticular
  2. Dense CT: More proteins & less ground subs.
    • 3 types: dense regular, dense irregular, elastic
24
Q

Loose CT; Areolar

A
  • contains fibroblasts, collagen & elastic fibres
  • Can be distorted w/out damage
    • provides shock absorption
  • found subcutaneous to skin
  • found nearly everywhere: surrounds nerves, blood vessels & individual muscle cells
25
Q

Loose CT; Adipose

A
  • known as “fat”
  • comprised mainly of adipocytes (fat cells) and little else (nuclei pushed to peripheral of cells
  • serves to pack around structures & provide padding, cushion shocks & acts as an insulator
  • if adipose cells increase fat stores = lipogenesis
    • if decrease fat stores = lipolysis

*Fat cells can NOT divide - mesenchymal cells provide extra fat cells if body has excess nutrients

26
Q

Loose CT; Reticular

A
  • contains reticular fibres, fibroblasts & leukocytes
  • found in spleen, lymph node & bone marrow
  • Provides structural support
27
Q

Dense Connective Tissue - characteristics

A
  • Is strong, has fibres (mostly collagen) packed tightly together
  • less ground substance than loose connective tissue
28
Q

3 types of dense connective tissue

A
  1. Dense regular CT
  2. Dense irregular CT
  3. Elastic CT
29
Q

Dense CT; Dense Regular

A
  • collagen fibres aligned parallel to applied force
  • found in tendons (muscle to bone) and ligaments (bone to bone)
  • few blood vessels - takes long time to heal following injury (rich blood supply necessary for good healing)
30
Q

Dense CT; Dense Irregular

A
  • bundles of collagen fibres extending in different directions
  • found in deep portions of skin (dermis) & capsules around organs such as liver, kidney & spleen
    • forms supporting layer around cartilage & bone (except in joints)
  • In places where you’d need to deal with forces from different directions.
31
Q

Dense CT; Elastic CT

A
  • predominantly elastic fibres that provide ability to stretch and recoil
  • found in voal cords & large/medium arteries & suspensory ligament of penis
32
Q

Two cell groups in CT proper

-examples (4 in each)

A
  1. Resident cells (permanently in CT)
    - Fibroblasts: most abundant in CT proper; produces fibres & ground sub. components of ECM
    - Adipocytes - small clusters or as adipose tissue (if large cluster)
    - Fixed macrophages - large irregular cells which phagocytose dead cells or pathogens - release chem. which stimulate immune response
    - Mesenchymal cells - embryonic stem cell - differentiates into required CT cell
  2. Wandering Cells - primarily Leukocyte type (WBC) [no. at particular moment depends on local conditions]
    - mast cells: usu found close to blood vessels - involved in clotting and dilation of vessels
    - plasma cells: synthesises disease fighting proteins called antibodies - usu found in intestinal walls, spleen & lymph node
    - free macrophages: mobile phagocytic cells that are formed from monocytes; engulf and destroy and bacteria, foreign particles or damaged cell/debris
    - Other leukocytes migrate through blood vessel - majority = neutrophils (seeks out bacteria)
33
Q

Fibres of Connective Tissue Proper (3)

A
  • produced by CT cells and secreted in ECM
    1. Collagen Fibres: long, unbranching, strong, flexible and resistant to stretching; make up 25% of all protein; found in ligaments & tendons - parallel struct. allows them to withstand enormous force in that direction
    2. Elastic Fibres: thinner than collagen, stretch easily (due to coiled struct.), branch & then rejoin; allow structures (blood vessels, skin, lungs, arteries) to stretch & relax
    3. Reticular Fibres: thinner than collagen, form a meshwork-like configuration; act as packing material & provide structural support for certain organs. Found in organs w/ abundant spaces: liver, lymph nodes & spleen
34
Q

Ground substance of Connective Tissue Proper

A
  • Is a colourless, featureless, viscous solution that has a gelatinous, rubbery consistency
  • Is a combo of proteins and carbs
    • additional content such as H2O & salts can result in texture that is semi-fluid to hard
35
Q

Two Types of supporting Connective Tissue (identify only)

A
  1. Cartliage

2. Bone

36
Q

4 Components of Fluid Connective Tissue

A
  1. Plasma: watery ground subs. containing protein fibres
  2. Erythrocytes: red blood cells
  3. Leukocytes: White blood cells
  4. Platelets: Fragments of blood cells involved in blood clotting
37
Q

Muscle tissue - composition & basic outline as to function

A
  • Comprised of cells called fibres

- When stimulated by nervous system, fibres shorten or contract - resulting in movement

38
Q

3 Types of Muscle

A
  1. Skeletal: multinucelated, long cylindrical, striated fibres
    • moves skeleton
    • Responsible for voluntary body movement
    • attaches to bone or skin - found in voluntary sphincters
  2. Cardiac: one/two nuclei, short bifurcated and striated fibres w/ intercalated discs
    • involuntary contractions & relation pump blood in heart (heart wall - myocardium
  3. Smooth: non sriated, spindle shaped (fusiform) w/ central nucleus
    • involuntary movements and motion
    • found in walls of internal organs - vessels, airways, bladder, stomach, uterus
      - helps propel & control movement of material through these organs
39
Q

2 types of Cell in Nervous Tissue

-function of nervous tissue

A
  1. Neurons: nerve cells that are capable of initiating and conducting electrical activity throughout body
    • are the longest cell in the body
  2. Neuroglia: cells that support the neurons (are a supportive network)

*Function: communication and control of body function

40
Q

Body Membranes - where they are

-4 Types

A

-Found in major body cavities that line the internal and external cavity surfaces.

Types;

  1. Mucous
  2. Serous
  3. Cutaneous
  4. Synovial
41
Q

Mucous Membranes (Mucosa)

  • where
  • roles
A
  • Lines body passageways
  • connective tissue - lamina propria
  • Has absorptive, secretory and protective roles
  • mucous cells prevent drying out - lubricate and trap foreign substances
  • Found: digestive, respiratory, reproductive and urinary tracts
42
Q

Serous Membranes (Serosa)

  • composed of
  • where found
A
  • simple squamous epithelium - mesothelium
  • Parietal and visceral serous layers
  • Found; pleura (around lungs), pericardium (around heart) & peritoneium (around abdomin)
43
Q

Cutaneous membranes (skin)

A
  • largest membrane in body
  • keratinised stratified squamous epithelium
  • connective tissue - dermis (also w/ epidermis)
  • protects body from external enviro & prevents water loss
44
Q

Synovial membranes - joint lining

A
  • composed of well-vascularised areolar, fibrous or adipose connective tissue
  • secretes synovial fluid that reduces joint friction and provides nutrients to the joint surfaces