ToB S2 - Glands and External Surfaces

Question 1

Define the term gland

Answer 1

Specialised cell, group of cells, or organ of endothelial origin that selectively removes materials from the blood, concentrates or alters them, and secretes them for further use in the body or for elimination from the body

Question 2

How are glands classified by the destination of secretion?

Answer 2

1) Exocrine - glands secretes into ducts
2) Endocrine - glands are ‘ductless’, secrete directly into bloodstream or lymphatic vessels

Question 3

Name three types of secretory methods

Answer 3

1) Holocrine
2) Merocrine
3) Apocrine

Question 4

Describe holocrine secretion

Answer 4

Holocrine secretions are produced in the cytoplasm of the cell and released by the rupture of the plasma membrane, which destroys the cell and results in the secretion of the product into the lumen

Question 5

Describe merocrine secretion

Answer 5

Merocrine secretions are those that are secreted by exocytosis. There is NO loss of cell and is the most common form of secretion

Question 6

Describe apocrine secretion

Answer 6

Relating to or denoting multicellular glands which release some of their cytoplasm in their secretions, especially the sweat glands associated with hair follicles in the armpits and pubic regions.

Question 7

Describe the mechanism of endocytosis

Answer 7

• Endocytosis is the process of engulfing material initially outside the cell.
• Vesicle engulfed into the cell by fusing with plasma membrane and budding off in the cytoplasm

Question 8

Why is glycosylation of newly synthesised proteins in the Golgi so important?

Answer 8

O-linked glycosylation of proteins, by glycosyl transferase, using the addition of complex branching sugars, produces glycoproteins that form the glycocalyx on the cell surface membrane Glycocalyx is needed for:

• Adhesion to substrates and neighbouring cells
• Mobility of cells
• Communication with neighbouring cells

Question 9

Name three secretions from the exocrine pancreas

Answer 9

• Trypsinogen
• Pancreatic amylase
• Lipase

Question 10

Describe simple mechanisms that control secretions

Answer 10

There are 4 main mechanisms

1) Nervous control - Adrenaline rerelease from adrenal medulla stimulated by sympathetic nervous stimulation
2) Endocrine control - ACTH stimulates the cortex of the adrenal gland to secrete cortisol
3) Neuro-endocrine control - Nervous cells of the hypothalamus control ACTH secretion from the anterior pituitary
4) Negative feedback chemical mechanism - Inhibitory effect of high T3 and T4 levels on TSH synthesis by the anterior pituitary gland

Question 11

What does a mucous membrane consist of?

Answer 11

1) An epithelium (type depending on site) lining the lumen of a tube
2) An adjacent layer of connective tissue often referred to as the lamina propria
3) In the alimentary tract, a third layer consisting of smooth muscle cells referred to as the muscularis mucosae

Question 12

What does a serous membrane consist of?

Answer 12

These are thin two-part membranes that line certain closed body cavities. They envelop the viscera (hand in balloon)

1) A simple squamous epithelium (mesothelium), which secretes a watery lubricating fluid
2) A thin layer of connective tissue which attaches to epithelium to adjacent tissues (also carries blood vessels and nerves)

Question 13

Name an exocrine gland

Answer 13

Any from:

• Goblet cells
• Parotid glands
• Submandibular glands

Question 14

Name an endocrine gland

Answer 14

Any from:

• Pancreas
• Thyroid gland
• Parathyroid glands
• Adrenal glands

Question 15

Describe the structure of the alimentary tracts

Answer 15

1) The mucosa (innermost layer)
2) The submucosa (areolar connective tissue)
3) Muscularis externa (peristalsis)
4) The serosa (serous membrane)

Question 16

Describe the structure of the oesophagus

Answer 16

1) Non-keratinised stratified squamous epithelia
2) Lamina propria - loose connective tissue bearing blood and lymph vessels, some smooth muscle and many cells of the immune system
3) Muscularis mucosa - the thin layer of smooth muscle cells
4) Submucosa - subtending layer of connective tissue containing mucus secreting glands
5) Muscularis externa - Smooth muscle layers (inner circular, outer longitudinal), which move food via peristalsis
6) Adventitia - thin outermost layer of connective tissue (no peritoneal enfolding of this portion of the GI tract)

Question 17

Describe the structure of the stomach

Answer 17

1) Epithelium - Simple columnar epithelia for absorption
2) Gastric mucosa - secretes acid, digestive enzymes and gastrin
3) Muscularis mucosa
4) Submucosa
5) Muscularis externa - three layers (oblique, circular and longitudinal) of smooth muscle
6) Rugae - Folds of the gastric mu

Question 18

What are the layers of the tracheal mucosae?

Answer 18

1) Pseudostratified ciliated epithelia
2) Submucosa
3) Fibroelastic membrane and tracheal muscle
4) C-shaped Hyaline cartilage
5) Adventitia

Question 19

What are the layers of the bronchioles?

Answer 19

1) Epithelia
2) Smooth muscle
3) Alveoli

Question 20

Where are the plicae circulares found?

Answer 20

Jejunum

Question 21

How many layers of muscularis externa are found in the bladder?

Answer 21

3 - inner circular, outer longitudinal and oblique