Tissues

Question 1

Define Tissue

Answer 1

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)

Question 2

4 Types of Tissues

Answer 2

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

Question 3

Epithelial Tissue - 6 General characteristics

Answer 3

• 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

Question 4

4 Functions of Epithelial Tissue

Answer 4

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

Question 5

Basement Membrane

Answer 5

• 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

Question 6

Intercellular Junctions - 4 types

Answer 6

*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

Question 7

Tight Junctions

Answer 7

• 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

Question 8

Adhering Junctions

Answer 8

• 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

Question 9

Desmosomes

Answer 9

• 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

Question 10

Gap Junctions

Answer 10

• 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.

Question 11

Epithelia Classification

Answer 11

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

Question 12

Epithelial Cell Shapes (3)

Answer 12

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)

Question 13

Epithelium Cell Layers (3)

Answer 13

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)

Question 14

Types of Epithelium & Location (Simple)

Answer 14

• 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

Question 15

Types of Epithelium & Location/function (Stratified)

Answer 15

• 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

Question 16

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

Answer 16

• 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

Question 17

Glands - Function

-2 Categories

Definition of Duct

Answer 17

• 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

Question 18

Connective Tissue - Overview

Answer 18

• 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

Question 19

3 structural components of Connective Tissue

Answer 19

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

Question 20

Protein fibres in CT (3)

Answer 20

• Elastic fibres
• collagen fibres
• Reticular fibres

Question 21

6 Functions of connective tissues

Answer 21

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

Question 22

3 Broad classifications of Connective Tissues

Answer 22

1. CT Proper
2. Supporting CT
3. Fluid CT

Question 23

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

Answer 23

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

Question 24

Loose CT; Areolar

Answer 24

• 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

Question 25

Loose CT; Adipose

Answer 25

- 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

Question 26

Loose CT; Reticular

Answer 26

- contains reticular fibres, fibroblasts & leukocytes - found in spleen, lymph node & bone marrow - Provides structural support

Question 27

Dense Connective Tissue - characteristics

Answer 27

- Is strong, has fibres (mostly collagen) packed tightly together - less ground substance than loose connective tissue

Question 28

3 types of dense connective tissue

Answer 28

1. Dense regular CT 2. Dense irregular CT 3. Elastic CT

Question 29

Dense CT; Dense Regular

Answer 29

- 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)

Question 30

Dense CT; Dense Irregular

Answer 30

- 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.

Question 31

Dense CT; Elastic CT

Answer 31

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

Question 32

Two cell groups in CT proper | -examples (4 in each)

Answer 32

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)

Question 33

Fibres of Connective Tissue Proper (3)

Answer 33

* 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

Question 34

Ground substance of Connective Tissue Proper

Answer 34

- 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

Question 35

Two Types of supporting Connective Tissue (identify only)

Answer 35

1. Cartliage | 2. Bone

Question 36

4 Components of Fluid Connective Tissue

Answer 36

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

Question 37

Muscle tissue - composition & basic outline as to function

Answer 37

- Comprised of cells called fibres | - When stimulated by nervous system, fibres shorten or contract - resulting in movement

Question 38

3 Types of Muscle

Answer 38

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

Question 39

2 types of Cell in Nervous Tissue -function of nervous tissue

Answer 39

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

Question 40

Body Membranes - where they are -4 Types

Answer 40

-Found in major body cavities that line the internal and external cavity surfaces. Types; 1. Mucous 2. Serous 3. Cutaneous 4. Synovial

Question 41

Mucous Membranes (Mucosa) - where - roles

Answer 41

- 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

Question 42

Serous Membranes (Serosa) - composed of - where found

Answer 42

- simple squamous epithelium - mesothelium - Parietal and visceral serous layers - Found; pleura (around lungs), pericardium (around heart) & peritoneium (around abdomin)

Question 43

Cutaneous membranes (skin)

Answer 43

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

Question 44

Synovial membranes - joint lining

Answer 44

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