Epithelial Tissue- Week 7

Question 1

Explain the functions of epithelial tissue (6 points)

Answer 1

-provide physical protection(i.e. epithelial tissue on the epidermis on skin)
-control permeability(selectively filter e.g. alveoli and capillaries)
-provide sensation(sensory epithelium which contain sensory cells-nose, ears..)
-absorb nutrients(i.e. in digestive tract)
-secretion(glandular epithelium- hormones)
-transport (ciliated epithelia sweep mucus, cells)

Question 2

Name the 5 characteristics of epithelial tissue

Answer 2

1) Polarity: have apical & basal surfaces
2) specialised contacts: refers to cell junctions
3) Attachment: means epithelial cells are attached via basement membrane to underlying connective tissue
4) Avascularity: epithelial tissue doesn’t contain any blood vessels
5) Regeneration: epithelial tissue can quickly replace lost cells by division from stem cells

Question 3

Name the classes of epithelial tissues and briefly describe structures and functions of each simple epithelial cells

Answer 3

• Simple Squamous Epithelium: single layer of flat cells with disc-shaped nuclei, allows material to pass by Diffusion & Filtration
• Simple Cuboidal Epithelium: single layer of cube-like cells with large spherical central nuclei, function; secretion & absorption
  -Simple Columnar Epithelium: single layer of tall cells with oval nuclei (some have cilia or microvilli). Function; Absorption of nutrients for Ciliated type its to Move material

Question 4

Name the classes of epithelial tissues and briefly describe structures and functions of each stratified epithelial cells

Answer 4

• Stratified Squamous Epithelium: (2 types: non keratinised & keratinised type), thick several layers of flat cells, not all cells tuch the basal membrane, Function; Protects underlying tissues against pathogens..
  -Stratified Cuboidal Epithelium: usually two layers of cuboidal cells, Function; Secretion of substances i.e. sweat glands
  -Stratified Columnar Epithelium: several layers which the basal cells are cuboidal & columnar, Function; Secretion & protection

Question 5

what are the 2 types of epithelial cells that don’t fit in any of the classes of epithelial tissues

Answer 5

-Pseudostratified Columnar Epithelium
-Transitional Epithelium

Question 6

describe what Pseudostratified Columnar Epithelium is and its functions and locations

Answer 6

Description: single layer of cells (some tall, some short) ALL in contact with basement membrane
Function: Secrete substances particularly mucus, Movements of mucus by ciliary action
Location: lines male reproductive tract & respiratory system (e.g. trachea)

Question 7

describe what Transitional Epithelium is and its functions and locations

Answer 7

Description: several cell layers, basal cells are cuboidal or columnar, surface cells dome shaped or flat
Function: Stretches to permit distention of urinary bladder.
Location: lines urinary bladder

Question 8

Describe classification of glands on the basis of site of product release

Answer 8

can be classified as Endocrine or exocrine as well they can be classified on the number of cells forming the gland: can be Unicellular (made up of 1 cell) or Multicellular (several cells)

Question 9

what does endocrine release mean

Answer 9

internally secreting- substances gets released in the extracellular space between epithelial cells

Question 10

what does exocrine release mean

Answer 10

externally secreting- the products are externally secreted- can be on the skin really outside or inside body cavities like the stomach

Question 11

Explain the function of glands

Answer 11

they are specialised epithelial tissue structures that secrete substances, e.g. mucin-goblet cells are a gland, hormones-thyroid glands & adrenal gland, enzymes-pancreas produces& secretes digestive enzymes

Question 12

Describe the mode of secretion of merocrine, apocrine and holocrine glands

Answer 12

• Merocrine Glands: most-secrete products by exocytosis (sweat glands, salivary glands)
  *Apocrine Glands: a portion of plasma membrane buds off the cell, containing the secretion (mammary glands)
  *Holocrine Glands: the entire cell disintegrates to secrete its product

Question 13

what are the different ways of staining methods

Answer 13

• Histology
• Histochemistry
• Immunohistochemistry

Question 14

For Histology staining explain what do the Basic and Acidic dyes stain and why that happens

Answer 14

-basic dyes stain acidic structured: haematoxylin binds to nuclear DNA & RNA
-Acidic dyes stain alkaline structures: Eosin binds to proteins in the cytoplasm

Question 15

for Histology staining explain the different colour stains

Answer 15

-aniline blue: Collagen Blue
-Biebrich Scarlet: Cytoplasm Red
-Haematoxylin: Nuclei Dark Blue

Question 16

what does Histochemistry staining identify

Answer 16

identification of macromolecules (DNA, RNA, Carbohydrates, lipids) & chemical compounds (calcium, sodium) in cells & tissues

Question 17

how does Histochemistry staining work and what colour is the stain

Answer 17

Periodic Acid Schiff (PAS):
1)detects carbohydrate macromolecules, like glucose & macro substances like glycoproteins
2) periodic acid oxidises sugars & exposes aldehyde groups, which these react with the Schiff reagent to give a PURPULE-MEGANTA colour

Question 18

how does immunohistochemistry staining work

Answer 18

-use antibodies to detect & localise specific proteins
- antibody-antigen specific interaction
- antibodies conjugated with fluorescent dyes

Question 19

Name the type of epithelium that would be in these locations

1.Blood vessels

2.Small endocrine ducts

3.Lining the bronchus

4.Oral cavity / oesophagus

5.Vas deferens

6.Oviduct

7.Lining of the gastrointestinal tract

8.Skin

9.Nephrons of kidney

10.Lung alveoli

Answer 19

1.Simple squamous
2.Simple cuboidal
3.Pseudostratified columnar
4.Stratified squamous
5.Pseudostratified columnar
6.Simple columnar
7.Simple columnar
8.Stratified squamous
9.Simple cuboidal
10.Simple squamous

Question 20

Which of these best describes the epithelium of the skin?

1) Simple squamous
2) Stratified squamous
3) Simple cuboidal
4) Stratified cuboidal
5) Columnar

Answer 20

2

Question 21

Name the principle cells of the liver. ________

Name one function carried out by these cells. ________

Answer 21

1. hepatocyte, hepatocytes
2. storage, secretion, degradation, metabolism, produce urea, synthesis, detoxification

*The hepatocytes have several functions:-

Store glycogen and break it down to regulate blood sugar (regulate metabolism)

Synthesise, absorb and degrade cholesterol Metabolise amino acids to produce urea

Degrade toxins (detoxification)

Secrete plasma proteins (into blood) and bile (into bile ducts)

Question 22

In a pseudostratified epithelium

1. Only the bottom layer of cells is in contact with basement membrane
2. All cells are in contact with the basement membrane
3. All cells are in direct contact with loose connective tissue
4. Only the bottom layer of cells is in contact with loose connective tissue
5. None of the above

Answer 22

2

*pseudostratified epithelium is a single layer of cells, all of which contact the basement membrane.

Question 23

What is the very thin, specialised epithelium of the blood vessels and vascular system called?

Answer 23

Endothelium, endothelium

Question 24

what is the difference between cilia and microvilli

Answer 24

Cilia (10 micrometre) follow a rhythmic movement or movement of cells over the object while microvilli (1 micrometre) just enhance the absorption of nutrients by increasing its surface area

Question 25

A common feature of epithelial cells is:-

1. Absence of blood vessels

2.Direct contact to the submucosa layer

3. The presence of an arteriole blood supply
4. The absence of a basement membrane

5.The delivery of nutrients by active transport

Answer 25

1