Gland Structure and Function

Question 1

Define gland.

Answer 1

An epithelial cell or an aggregate (usually and aggregate) of epithelial cells that are specialised for the secretion of a substance.

Question 2

What are the main differences between endocrine glands and exocrine?

Answer 2

Endocrine are ductless and secrete its product into the blood system to let the secreting function at a distant part of the body. (hormones) ALL EPITHELIAL CELLS SECRETE THE HORMONES IN THE GLAND.
Exocrine are ducted and secrete its product into a duct, they are more generally more local and its product is generally enzymes or lubricants. ONLY THE CELLS AT THE APEX OF THE DUCT SECRETE THE PRODUCT.

Question 3

What are some examples of endocrine glands and what are their hormones?

Answer 3

Anterior pituitary gland (ACTH, LH, FSH and TSH)
Posterior pituitary gland (ADH and oxytocin)
Thyroid gland (T3, T4 and calcitonin)
Parathyroid gland (PTH)

Question 4

What are some examples of exocrine glands and what are their products?

Answer 4

Salivary glands (amylase e.g.)
Pancreas (amylase, trypsin, lipase) (also endocrine)
Sweat glands (sweat)
Sebaceous gland (secrete sebum (oil))

Question 5

Give the steps of the generation of a gland.

Answer 5

1. Growth signal received
2. Proliferation of cells.
3. Epithelial cells invade the space created
4. In exocrine glands the central cells die off to produce a duct
5. in endocrine glands angiogenic factors produce blood vessels around the epithelial cells.

Question 6

What are the two main shapes of gland ducts?

Answer 6

Simple duct structure and compound duct structure.

Question 7

What are the subtypes of simple duct structure? Give examples of each.

Answer 7

Simple tubular (intestinal glands)
Simple branched tubular (gastric glands)
Simple alveolar (none important in humans)
Simple branched alveolar (sebaceous glands)

Question 8

What are the subtypes of compound duct structure?

Answer 8

Compound tubular (duodenal glands and small intestinal)
Compound alveolar (mammary glands)
Compound tubuloalveolar (salivary glands)

Question 9

What are myoepithelial cells?

Answer 9

Cells that have features of both an epithelial cell and a smooth muscle cell. This means they help ejecting secretions from the duct.

Question 10

What are the different mode of secretions?

Answer 10

Merocrine
Apocrine
Holocrine
Cytocrine

Question 11

Explain merocrine and give an example.

Answer 11

Fusion of vesicles with the apical membrane and the product is then released. It is a form of exocytosis. An example is insulin release of endocrine glands of the pancreas.

Question 12

Explain apocrine and give an example.

Answer 12

A part of the gland is ‘pinched’ off. A partial loss of cytoplasm.
E.g. mammary glands and sweat glands.

Question 13

Explain holocrine and give an example.

Answer 13

Complete loss of cytoplasm or cell.

E.g. sebaceous gland in skin and tarsal glands in eyelid.

Question 14

Explain cytocrine and give an example.

Answer 14

The entire cell is released as a secretion.

E.g. spermatid.

Question 15

What is the main difference between regulated secretion and constitutive secretion?

Answer 15

Regulated happens due to a trigger like calcium ions.

Constitutive happens all the time without any trigger.

Question 16

Give an example of regulated secretion.

Answer 16

Eating a breakfast leading to insulin secretion.
Glucose is broken down to ATP
ATP closes K+ channels means K+ can’t leave. Membrane depolarisation occurs and calcium channels open so Ca2+ enters cell.
Ca2+ helps with the regulated secretion and insulin is released.

Question 17

Outline the steps of holocrine secretion.

Answer 17

1. Secretory cell fills up with secretory granules
2. Cell organelles degenerate
3. Cell dies
4. Plasma membrane breaks and the contents empty
5. Dead cells are replaced by mitotic division of basal cells.

Question 18

What is the main function of the Golgi in secretion?

Answer 18

Glycosylation of proteins

Question 19

What is glycosylation of proteins?

Answer 19

The covalent attachment of sugars by enzymes to proteins and lipids to form glycoproteins and glycolipids.

Question 20

Why is glycosylation important?

Answer 20

It aids protein folding
Prevents protein digestion intracellularly
Prevents lipid digestion intracellularly
Cell recognition
Role on cell to ECM attachment

Question 21

What is phagocytosis?

Answer 21

Where cells (phagocytes) engulf other cells or particles
Mainly used by the immune system.

Question 22

What is pinocytosis?

Answer 22

Where cells ingest liquid droplets. (used by all cells)

Question 23

What is transcytosis?

Answer 23

When a particle move from lumen to interstitium via or between epithelia.

Question 24

What are the 4 examples of transcytosis?

Answer 24

1. Through aqueous channels in the intercellular junction
2. Lipid cell membranes (diffusion across)
3. Transport via carrier proteins
4. Endocytosis and then exocytosis

Question 25

What are the 3 controls of gland secretion and what are they primarily regulated by?

Answer 25

Hormonal, Neural and Humoral.

Controlled by negative feedback

Question 26

How does hormonal control of gland secretion work?

Answer 26

Hypothalamus secrete hormone that tells anterior pituitary gland to secrete a hormone. The hormone secreted the anterior pituitary then tells a peripheral endocrine gland to secrete its hormone. This hormone then arrives to its target cell and an action is performed.

Question 27

How does neural control of gland secretion work?

Answer 27

Nervous system tells an endocrine gland to release a hormone. Hormone arrives to target cell and an action is performed.

Question 28

How does humoral control of gland secretion work?

Answer 28

A changed level of a substance in the plasma activates an endocrine gland. Endocrine gland secretes hormone and it targets a cell. Cell produces a response.