lecture 3

Question 1

what is a gland

Answer 1

it is an epithilial cell, or collection of cells specialised for secretion

Question 2

what is exocrine

Answer 2

a gland with a duct that secretes to an epithilial surface

Question 3

what is endocrine

Answer 3

a ductless gland, where hormones secrete into the bloodstream

Question 4

mucous gland secrete

Answer 4

mucus. stain poorly in H&E (light)

Question 5

serous gland secrete

Answer 5

enzyme, watery, no mucus. stain pink in H&E

Question 6

merocrine secretion. an example and what is it

Answer 6

exocytosis product in a vesicle approaches cell surface continuity between vesicle and membrane- transiently larger salivary glands/ sweat gland

Question 7

apocrine secretion

Answer 7

endocytosis non membrane structure e.g lipid approaches cell surface makes contact and pushes through apical membrane the apical (lumenal) cytoplasm pinches off membrane transiently smaller e.g. mammary glands

Question 8

what are myoepithilial cells

Answer 8

contraction pushes lumenal content towards duct e.g. secretion of milk from acini

Question 9

holocrine secretion

Answer 9

disintegration of cell to release contents e.g. sebaceous gland to fill hair follicle with sebum

Question 10

what is endocytosis

Answer 10

engulf material initially on the outside of the cell It is the opposite of exocytosis (merocrine secretion). Endo/Exocytosis are coupled in transepithelial transport.

Question 11

describe how endocytosis and secretion combine to give transepithelial transport

Answer 11

When a molecule is too large to penetrate membranes it can be shunted across from one component of the body to another. - Material is endocytosed at one surface of the cell - The transport vesicle shuttles it across the cytoplasm - The material/vesicle is then exocytosed at the opposite surface.

Question 12

Golgi Apparatus – Structure:

Answer 12

• Stack of disc-shaped cisternae - One side of the discs are flattened, other side is concave - Discs have swelling at their edges (Vesicles that bud off) - Distal swellings pinch off as migratory Golgi Vacuoles

Question 13

Golgi Apparatus – Function:

Answer 13

compartmentalise

Packaging through condensation of contents

Glycosylation

Transport

Question 14

Golgi Apparatus – Product Destinations:

Answer 14

• Majority extruded in secretory vesicles - Some retained for use in the cells (eg lysosomes) - Some enter the plasma membrane (Glycocalyx)

Question 15

Golgi Apparatus – Glycosylation & Specificity

Answer 15

• Branching sugars offer:

complex shapes for specific interactions in the glycocalyx

Enzymatic destruction of this layer alters specificity

Adhesion to substrates & neighbouring cells - Communication with neighbouring cells -

Mobility of cells .

Question 16

Describe simple mechanisms of control secretion

Answer 16

Nervous Control - e.g. sympathetic nervous stimulation of adrenal medullary cells leads to the release of adrenaline. Endocrine control – e.g. adrenocorticotrophic hormone (ACTH) stimulates the cortex of the adrenal gland to secrete hormones (e.g. Cortisol) Neuro-endocrine control – e.g. nervous cells of the hypothalamus control ACTH secretion from the anterior pituitary gland Negative feedback chemical mechanism – e.g. the inhibitory effect of high thyroxine (T3 & T4) levels on TSH synthesis by the anterior pituitary gland.

Question 17

classify gland by structure

Answer 17

secretory part: uni/multicellular

acinar(bulbous)/ tubular

coiled/branched

duct: simple/ coumpound

Question 18

what is the faulty gene in CF and where is it located

Answer 18

cystic fibrosis transmembrane regulator on apical membranes of epithilial cells

Question 19

what is the cause of cystic fibrosis

Answer 19

the CFTR is absent on apical membranes. cl transport is comprimised. na transport is comprimised (more in cell) water doesnt leave epithilium. mucus is viscous. cant be moved to oropharynx for swallowing. pulmonary infection

Question 20

what is meconium ileus

Answer 20

when babies cant pass first stool.

CF causes viscous mucus in GI tract. less easy to pass stool.

constipation and invagination of GI tract in older patients

Question 21

why is sweat testing indicative of CF

Answer 21

no CFTR on apical membrane of epithilial cells lining the sweat gland duct. poor reabsorption of cl ions sweat is rich with cl and na. very salty

Question 22

describe thyroid follicle and production of hormones

Answer 22

a follicle contains the colloid and the simple cuboidal epithilium surrounding it

SC synthesis and secrete thyroglobulin

simple cuboidal cells take up iodide from blood –> oxidise to iodine–> colloid

iodination of thyroglobulin occurs in colloid

forms thyroxine and tri-iodothyronine in colloid

t3 and t4 receptor mediated endocytosis into SC then exocytosis into capillary lumen bloodstream

Question 23

which cells do parathyroid glands have

Answer 23

chief cells with secrete parathyroid hormone, controls calcium