WEEK 5: ORGANISATION OF CELLS INTO TISSUES

Question 1

What is epithelial tissue?

Answer 1

Tightly-bound contiguous (adjoining) cells forming sheets covering the body surface or lining the body cavities and their invaginated glands.

Question 2

State the three embryonic layers epithelial tissues are derived from.

Answer 2

They are derived from the three embryonic layers (ectoderm, mesoderm and endoderm).

Question 3

State the characteristics of epithelial tissue.

Answer 3

1.Cells are tightly bounded together.

2.Little intercellular spaces and extracellular matrix.

3.Separated from the underlying connective tissue by basal lamina.

4.Avascular and it is nourished by diffusion from underlying tissues.

5.Have a high rate of regeneration.

Question 4

State the functions of epithelial tissue.(8)

Answer 4

1.Protection.

2.Trans-cellular transport.

3.Secretion.

4.Absorption.

5.Selective permeability.

6.Sensation.

7.Digestion.

8.Excretion

Question 5

State the different names which can be assumed by epithelium based on its location.

Answer 5

1.Epidermis for external surface.
2.Mesothelium for body cavities.
3.Endothelium for blood vessels.
4.Neuroepithelium.
5.Glandular epithelium.

Question 6

Describe how the epithelial tissues are named.

Answer 6

1.The first name indicates the number of cell layers present.
Simple- one layer
Stratified- more than one layer

2.The second describes the shape of its cells
Squamous, cuboidal, and columnar

Question 7

Single layer of flat cells with central nuclei.

Function:
Exchange of gases and fluids.

Sites:
Lung alveoli, endothelium, mesothelium, parietal layer of Bowman’s capsule and thin segments of loop of Henle.

What epithelium is this?

Answer 7

Simple squamous

Question 8

Single layer of tall cylindrical or hexagonal cells with oval basal nuclei.

Function:
Secretion, absorption, transport.

Sites:
Digestive tract & gall bladder (lined by microvilli), large ducts and female genital ducts & small bronchi (lined by cilia).

Answer 8

Simple columnar.

Question 9

Single layer of cells, all rest on basal lamina but not all reach to surface, with nuclei arranged in many rows.

Function:
Protection, secretion, absorption.

Sites:
Respiratory tract ( kinetic cilia - motile).
Epididymis & vas deferens (stereocilia -nonmotile)

What epithelium is this?

Answer 9

Pseudostratified Columnar

Question 10

Basal cells are cuboidal, next layers are polygonal, the surface cells are flattened.

Function:
protection.

Sites:
Epidermis (keratinized).
Oral cavity, oropharynx, esophagus & vagina (non-keratinized).

What epithelium is this?

Answer 10

Stratified squamous

Question 11

Two layers of cuboidal cells.

Function:
Transport and protection

Sites:
Duct of sweat glands. mammary glands, sweat glands, salivary glands, and pancreas.
Forms the lining of ovarian follicles and seminiferous tubules

What epithelium is this?

Answer 11

Stratified cuboidal

Question 12

Basal cells are cuboidal, next layers are polygonal, the surface cells are columnar.

Function:
Protection and transport.

Sites:
Conjunctiva of the eye.
Large ducts.
Parts of male urethra

What epithelium is this?

Answer 12

Stratified Columnar

Question 13

Resembles both stratified squamous and stratified cuboidal. Basal cells are cuboidal or low columnar, next layers are polygonal, the surface cells are columnar, dome-shaped binucleated (in empty bladder), but change to flattened cell in full bladder.

Function:
Protection, transport & adaptation for stretch.

Sites:
Urinary tract (calyces, renal pelvis, ureter, bladder and parts of urethra)

What epithelium is this?

Answer 13

Transitional epithelium

Question 14

State the 3 cell surfaces.

Answer 14

1.apical,
2.lateral and
3.basal surfaces

Question 15

State the 4 apical modifications.

Answer 15

1.Microvilli- They increase the surface area of the cell to increase its absorption.

2.Cilia- Cilia propel the mucus and other structure over the surface of the epithelium by rapid rhythmic oscillations.

3.Flagella- Present only in the spermatozoa

4.Cell coat (glycocalyx)

-Glycoprotein attached to the external surface of the cell membrane.

-Formed of carbohydrate chain attached to the transmembrane protein of the plasmalemma.

• Contains some hydrolytic enzymes and alkaline phosphatase.

-They function in protection and cell recognition.

Question 16

State the 4 main lateral modifications.

Answer 16

1.Occluding (tight) junction- Its function to prevent membrane proteins and water-soluble molecules from passing between the cells.

2.Adhering junction- .Function is not only joins the two cell membranes to each other, but also links the cytoskeleton of both cells.

3.Desmosome- Are weld-like junctions that help to resist the shearing forces.

Gap junction- They are tiny pores communicating between two adjacent cells and permit the passage of ions, amino acids, AMP and certain hormones between the cells.

-They are under regulation, so they may be opened or closed.

Question 17

State the 3 basal modifications.

Answer 17

1.Basement membrane.

2.Plasma membrane enfolding- Multiple basal enfolding of cell membrane to increase the surface area for transport.

3.Hemi-desmosome- Attach the basal cell membrane to the underlying basal lamina.

Question 18

Describe glandular epithelium.

Answer 18

Glands originate from the epithelial surface, penetrate the underlying connective tissue and manufacture a basal lamina around themselves.

Question 19

Outline the different ways of classifying glands.

Answer 19

1.MODE OF SECRETION

-Holocrine gland: The whole cell is destroyed and detached, e.g. sebaceous gland. (A)

-Merocrine gland: The cell is intact and it secretes through exocytosis of secretory vesicles, e.g. salivary glands. (B)

-Apocrine gland: the apical part of the cell is detached, e.g. mammary gland. (C)

2.TYPE OF SECRETION

-Mucous: sublingual (salivary), Brunner’s glands (in duodenum) and goblets cells.

Serous: parotid salivary gland.

Seromucous: Submandibular.

Waxy: ceruminous gland (external ear).

Fatty: sebaceous glands.

Watery: sweat glands.

Milk: mammary glands.

Cellular: testis

3.WAY OF SECRETION
number of secretory cells,

4.DUCT SYSTEM
- Exocrine gland: means it pours its secretion through duct system to a particular place, e.g. salivary glands.

-Endocrine gland: has no ducts and it delivers its secretion directly to the blood stream, e.g. thyroid gland.

-Mixocrine gland: has both types, e.g. pancreas.

5.SHAPE OF SECRETORY UNITS

6.NUMBER OF CELLS

-Unicellular gland:
One cell only, e.g. goblet cells in the epithelium of mucosa of respiratory tracts and intestine.

Multicellular gland: Many cells and they pour their secretion into the duct system, e.g. salivary glands.

Question 20

what is connective tissue?

Answer 20

These tissues connect and support other tissues of the body.

Question 21

State the functions of connective tissue.

Answer 21

1.Mechanical support

2.Medium for exchange of nutrients & waste products

3.Energy store and thermal insulation

4.Defensive functions
a) Barrier b) Engulf bacteria
c) Antibodies

Question 22

Outline the connective tissue cells.
1.Resident cell population
2.Wondering cell population

Answer 22

1.Resident cell population
Fibroblasts
Macrophages
Adipose cells
Mast cells
Undifferentiated mesenchymal cells

2.Wondering cell population
Lymphocytes
Plasma cells
Neutrophils
Eosinophils
Basophils
Monocytes

Question 23

Outline the connective tissue fibers.

Answer 23

1.Collagen fibers –collagen
-. Collagen fiber formation involves events that occur both within and outside the fibroblast.

2.Reticular fibers –collagen
-Reticular fibers provide a supporting framework for the cellular constituents of various tissues and organs,

3.Elastic fiber ——-elastin
*Found in lungs, large arteries, ligamenta flava (connecting laminae of successive vertebrae)

Question 24

State the 3 specialized connective tissue.

Answer 24

Specialized Connective Tissue:
1.CARTILAGE
*Prevents bones from rubbing against each other

*Does not contain nerves or blood vessels.

*Receives nutrition from perichondrium

*Cells are chondrocytes, matrix is a gel of chondroitin sulfate, hyaluronic acid, and chondronectin plus fluid.

-Fluid gives nutrients to the chondrocytes, which live in pockets called lacunae

-Fluid allows cartilage to be resilient and withstand compression

*Hyaline
-Found as articular cartilage at end of long bones and joints and connects ribs to the sternum.
-Nose, trachea, larynx

*Elastic
-Similar to hyaline cartilage but contains elastic fibers
-Give it flexibility, ability to bend
Found in pinnae, ear canal, epiglottis

*Fibrocartilage
-Found between vertebrae, in pelvis, and in knee joint
-Thick bundles of collagen, but few chondrocytes

2.BONE
-Compact, Cancellous

3.BLOOD

Question 25

State the 2 types of Connective Tissue Proper.

Answer 25

1.Loose Connective Tissue
- supports structures that it surrounds
Areolar, Adipose, Reticular

2.Dense Connective Tissue

• highly fibrous (collagen); little vascularization ground substance, or cells; reinforces and binds structures
  Dense regular, Dense irregular, Elastic

Question 26

List the 3 types of connective tissue and state their functions.

Answer 26

AREOLAR: Filling of open spaces during trauma is called edema.
-Main cells are fibroblasts

ADIPOSE:
- Energy storage, insulator, shock absorber
-White fat: Found throughout body
-Brown:

*Found in newborns and hibernating animals

*Site of heat production, temperature regulation

RETICULAR
*Function is to form a stroma, scaffolding and provide structural support for other cell types

*Contains only one type of fiber: reticular fibers

Question 27

State the functions of the 3 types of connective tissue.

Answer 27

1.REGULAR
*Makes up tendons and ligaments, fascia
*Tightly packed, parallel collagen fibers
*Resists strong pulling forces in one direction.

2.IRREGULAR
*Found in dermis, organ capsules
*Forms tough capsule of joints.
*Sheets of collagen run or stacked in different directions.

3.ELASTIC
*Found in areas of the body that require stretching:
Stomach, large airways, artery walls, bladder, between vertebrae

*Beneath transitional epithelium in urinary tract
*High concentration of elastic fibers (more than collagen) that is extremely flexible.

Question 28

What is a membrane?

Answer 28

Thin, protective layers that line body cavities, separate organs and cover surfaces.

Epithelial sheet bound to underlying layer of connective tissue proper.

Question 29

State the 4 common epithelial membranes.

Answer 29

Mucous
Serous
Cutaneous
Synovial

Question 30

Describe mucous membrane.
Where is it found?
Type of epithelium
Functions?

Answer 30

1.Always found lining organs that have connection to outside environment.

Digestive, respiratory, urinary, and reproductive tracts

2.Epithelium: stratified squamous, simple columnar, transitional
Covers the lamina propria (areolar connective tissue)

3.Secretion: Produces mucus (exception: urinary tract)
-lubrication, defense, reduce friction

-Play role in monitoring and controlling what enters into body.

-Absorption: microvilli in digestive system

Question 31

Describe serous membrane.
Where is it found?
Epithelium?
Function?

Answer 31

-Line walls and cover organs that fill closed body cavities (organs in chest and abdomen)

-Continuous membrane sheet that is doubled over to form a parietal and visceral layer.

*simple squamous epithelium + loose connective tissue

*Fluid is found between the two serosal layers to reduce friction.

pleural, peritoneal, pericardial fluid

Large amount of fluid is called effusion.

Effusion in abdomen is termed ascites.

Adhesions are connections between parietal and visceral layers that form when the serous membranes are damaged.

Question 32

Describe the cutaneous membrane.
Epithelium?
Where is it found?

Answer 32

Perpetually exposed to environment.
*Composed of keratinized stratified squamous epithelium called epidermis

*Epidermis is attached to underlying dense irregular connective tissue called dermis.

Question 33

Describe synovial membrane.
Where is it found?
Epithelium?
Function?

Answer 33

*Line the joints cavities

*Contain no epithelium
composed exclusively of loose adipose connective tissue covered by collagen and fibroblasts

*Manufacture synovial fluid that fills the joint spaces and reduces friction and abrasion at the ends of bones

Question 34

Basal cells are cuboidal, next layers are polygonal, the surface cells are flattened.

Function:
protection.

Sites:
Epidermis (keratinized).
Oral cavity, oropharynx, esophagus & vagina (non-keratinized).

Question 35

Basal cells are cuboidal, next layers are polygonal, the surface cells are flattened.

Function:
protection.

Sites:
Epidermis (keratinized).
Oral cavity, oropharynx, esophagus & vagina (non-keratinized).