Epithelial Tissues

Question 1

3 germ layers of the embryo

Answer 1

ECTODERM - epidermis of skin and corneal epithelium of eye
MESODERM - Urinary tract, blood and lymphatic vessel lining, pericardial and pleural sac lining and peritoneal lining
ENDODERM - epithelial of respiratory tract, GI tract, liver, and many glands - thyroid, salivary

Question 2

Basement membrane

Answer 2

Thin, flexible, acellular layer - lies between epithelial cells and the subtending connective tissue
Consists of a basal lamina - laid down by the epithelial cells
Cellular and molecular filter
The degree to which malignant cells penetrate basement membrane is highly relevant to prognosis

Question 3

Simple Squamous Epithelium

Answer 3

• lining of blood and lymph vessels - ACTIVE TRANSPORT
• lining of body cavities (pericardium, pleura, peritoneum) - LUBRICATION
• respiratory epithelium - pulmonary alveoli - GAS EXCHANGE
• Bowman’s capsule and Loop of Henlé of kidney
• inner and middle ear

Question 4

Simple Cuboidal Epithelium

Answer 4

• thyroid follicles - HORMONE SYNTHESIS, STORAGE & MOBILISATION
• small ducts of many exocrine glands - ABSORPTION & CONDUIT
• kidney tubules - ABSORPTION & SECRETION
• germinal epithelium (surface of ovary) - BARRIER

Question 5

Simple Columnar Epithelium

Answer 5

• stomach lining & gastric glands - SECRETION
• small intestine & colon - SECRETION, ABSORPTION & LUBRICATION
• gallbladder - ABSORPTION
• large ducts of some exocrine glands
• oviducts - TRANSPORT
• uterus
• ductuli efferentes of testis

Question 6

Pseudostratified Epithelium

Answer 6

• lining of nasal cavity, trachea,bronchi and bronchioles - MUCUS SECRETION FOR PARTICLE TRAPPING AND REMOVAL
• epididymis - ABSORPTION
• ductus deferens - SECRETION AND COMDUIT
• lacrimal sac
• large excretory ducts

Question 7

Stratified Squamous Non-Keratinized Epithelium

Answer 7

• oral cavity
• oesophagus
• larynx
• vagina
• part of anal canal
• surface of cornea
• inner surface of eyelid
  PROTECTION AGAINST ABRASION ADN REDUCES WATER LOSS WHILST REMAINING MOIST

Question 8

Stratified Squamous Keratinised Epithelium

Answer 8

• surface of skin
• limited distribution in oral cavity
  PROTECTION AGAINST ABRASION AND PHYSICAL TRAUMA, PREVENTS WATER LOSS, PREVENTS INGRESS OF MICROBES, SHIELDS AGAINST UV LIGHT DAMAGE

Question 9

Transitional (Urinary) Epithelium

Answer 9

• renal calyces
• ureters
• bladder
• urethra
  DISTENSIBILITY, PROTECTION OF UNDERLYING TISSUES FROM TOXIC CHEMICALS

Question 10

Renewal rates of epithelium

Answer 10

Turnover differs depending on location and function - speeds up if injury occurs
Epidermis - from cell division in basal layer (differentiation, migration, keratinisation and death) to being sloughed off is ~ 28 days
Lining of the small intestine - replaced by regenerative cells in the base of the crypts every 4-6 days
Other epithelia only are renewed in adult hood if there is physical damage or acute toxic injury

Question 11

Microvilli

Answer 11

Apical extensions which greatly increase the surface area for selective absorption

Question 12

Stereocilia

Answer 12

• like very long microvilli

Have an absorptive function

Question 13

Cilia

Answer 13

• bigger than microvilli

9: 2 structure of microtubules

Question 14

Epithelia

Answer 14

Sheets of contiguous cells, of varied embryonic origin, that cover the external surface of the body and line internal surfaces