Epithelial Tissues

Question 1

What are mucous membranes? Where are they found?

Answer 1

They line certain internal tubes which open to the exterior e.g. Respiratory tract, urinary tract.

Question 2

What are the three layers of mucous membranes?

Answer 2

Lumen, epithelium, lamina propria, muscularis mucosae.

Question 3

What are serous membranes? What do they line?

Answer 3

Thin, two part membranes which line certain epithelium:
Peritoneum (abdominal organs)
Pleural sacs (lungs)
Pericardial sacs (heart)

Question 4

What are the two layers of serous membranes? Lumen…

Answer 4

Lumen, simple squamous epithelium, connective tissue.

Question 5

What is the name of the inner and outer membrane of serous membranes? What’s inbetween?

Answer 5

Inner - visceral serosa
Outer - parietal serosa
Inbetween - lubricating fluid

Question 6

What is the definition of epithelium? What are the three types?

Answer 6

Sheets of cells that cover the external surface of the body and line internal surfaces.
Mucous membrane, serous membrane, skin.

Question 7

What is basement membrane?

Answer 7

The thin layer between epithelium and connective tissue.

Question 8

What is basement membrane also known as?

Answer 8

Basal lamina

Question 9

Describe simple squamous epithelium, its locations and its functions.

Answer 9

One cell thick - THIN - helps with functions
Found in the lining of blood vessels, body cavities (serous membranes), respiratory tract, kidneys.
Functions: lubrication (body cavities), gas exchange, barrier (kidneys), active transport.

Question 10

Describe simple cuboidal, its locations and functions.

Answer 10

Cube like shape, however pentagons from a bird’s eye view.
Found in thyroid follicles, small ducts of exocrine glands, kidney tubules, surface of ovary.
Functions: absorption (kidneys), barrier/covering (ovary), hormone synthesis (thyroid).

Question 11

Describe simple columnar epithelium, locations, functions.

Answer 11

Tall, ‘column’ structures, often with microvilli.
Found in small intestine, colon, oviducts, gall bladder, stomach.
Functions: Absorption (GI tract), lubrication, secretion, transport.

Question 12

Describe pseudostratified epithelium, location, functions.

Answer 12

Every cell is attached to the basement membrane but may be different sizes, often with cilia.
Locations: lining of nasal cavity, trachea, bronchi.
Functions: Secretion, absorption, particle trapping.

Question 13

Describe non-keratinised stratified squamous cells, locations, functions.

Answer 13

Stratified = many cells.
Look similar to cubical but many cells.
Locations: oral cavity, vagina, anal cavity, surface of cornea, inner eyelid.
Functions: Protection against abrasion, reduces water loss to remain moist.

Question 14

Describe keratinised stratified squamous cells, and the difference between non-keratinised.

Answer 14

same as non-keratinised stratified squamous but outmost layers lose their nucleus and become stratified.
Found in skin, layer of dermis (connective tissue), lining of living epithelial cells followed by a layer of dead keratinised cells.

Question 15

Describe the different layers of the skin.

Answer 15

Dermis, basal layer, prickle cell layer, granular layer, stratum corneleum (horny layer).

Question 16

Describe the journey of cells from the basal layer to the stratum corneleum.

Answer 16

Keratinocyte mitosis occurs in the basal layer
Daughter cells move up to he prickle cell layer, where they lose their ability to divide
they then synthesis into KERATIN, contributes to strength (found in hair and nails)
In the granular layer, cells lose their plasma membrane (phospholipid bilayer) and begin differentiating into CORNEOCYTES (found in stratum corneleum)
In granular layer, there are hundreds of KERATOHYLALIN GRANULES, which contain keratin and enzymes which degrade the phospholipid bilayer

Question 17

What are melanocytes?

Answer 17

Dendritic cells, occur. Along the basal layer of epithelium and produces melanin (pigment).
In darker people, there aren’t more melanocytes but they do secrete more melanin.

Question 18

What are langerhan cells?

Answer 18

Also dendritic cells, originate in the bone marrow.

Scattered in the prickle cell layer, intermediate immune responses by presenting antigens to T-lymphocytes.

Question 19

What is transitional epithelium? Locations and functions.

Answer 19

Stratified epithelium that transitions from a ‘relaxed’ to ‘stretched’ state. Found in the bladder, ureter and urethra, protects tissue from toxic chemicals.