L5- Glands introduction Flashcards
1
Q
definition of a gland
A
‘An epithelial cell or an aggregate of epithelial cells that are specialised for the secretion of a substance’
2
Q
secretion
A
production and release of materials by a cell or aggregate of cells
3
Q
types of gland
A
endocrine and exocrine
4
Q
glands are typically classified according to
A
their structure and how the products are released
5
Q
endocrine
A
ductless
- secrete directly into the blood flowing through them
6
Q
exocrine
A
ducted
- secrete into a location or region of the body through a duct
7
Q
what do endocrine glands secrete
A
hormones
- that work at distant parts of the body
8
Q
what do exocrine glands secrete
A
enzyme and lubricants
9
Q
name three endocrine glands
A
1) Pituitary gland
2) Thyroid gland
3) Parathyroid gland
10
Q
where is the pituitary gland found
A
the hypothalamus (beneath the thalamus)
11
Q
what does the anterior pituitary gland produce
A
hormones that regulate most of the glands of the endocrine system
e.g. ACTH LH FSH TSH Prolactin Somatorophin
12
Q
prolactin
A
stimulates milk production in mothers
13
Q
somatorophin
A
regulates growth of the body and tissue
14
Q
what does the posterior pituitary gland produce
A
- vasopressin (ADH)
- Oxytocin
15
Q
vasopressin (ADH)
A
prevents water loss from the kidney
16
Q
Oxytocin
A
that signals for delivery in pregnant women at the end of gestation and ejection of milk during breast feeding
17
Q
thyroid gland produces
A
thyroid hormone- T3 and T4
18
Q
T3 and T4
A
control metabolism, calcitonin (calcium homeostasis)
19
Q
parathyroid produces
A
produced parathyroid hormones, calcium homeostasis
20
Q
example of exocrine cells
A
- salivary gland
- pancreas gland
- mammary gland
- sweat glands
- sebaceous gland
- lachrymal gland
21
Q
generation of gland- in utero development
A
- Growth signal received (FGF family member)
- Proliferation of [daughter] cells occurs and extracellular protein degradation of enzymes produced
- Epithelial cells invade space created
a. Exocrine glands
i. Central part dies off to produce duct (canalicularisation)
b. Endocrine glands
i. Produce angiogenic factors to stimulate blood vessel growth in and around the epithelial cells
ii. Link to [mother] cells broken through apoptosis
22
Q
in thyroid follicles (endocrine) production of colloid between epithelial cells causes
A
expansion of follicle into a sphere
23
Q
endocrine glands are surrounded by
A
capillaries- quick transport fo hormones into the blood and to distant tissues
24
Q
hormone release in endocrine cells
A
directly released from cells e.g. B cells- insulin
25
release of enzymes and lubricants from exocrine cells
secretory cells form an acids (circle shape)- all cells secrete into the acinus and the product from many cells gets released from a single duct
26
two types of cells in exocrine glands
epithelial
- cells lining the duct
- cells that make secretly products
27
some cells at the end of the ducts change morphology and class by turning into
myoepithelial cells
28
myoepithelial cells
have features of both epithelial and smooth muscle cells
| - help eject sections from the duct
29
types of duct structure
tubular
alveolar
compound
simple
30
simple
duct does not branch e.g. intestinal glands
31
compound
duct branches
32
tubular
tube shaped
33
alveolar
rounder
34
salivary glands structure
compound tubuloalveolar
- branched
-
35
exocrine glands have two types of secretions
mucous
serous
36
development of the breast tissue starts
in utero
| - development then stops until puberty
37
At puberty what restarts breast development
oestrogen and progesteron
38
what stimulates the production of milk in pregnancy
prolactin (colostrum and milk)
39
oestrogen stimulates
formation of terminal end bulbs in prepuberty
40
oestrogen and progesterone in puberty
ductal elongation
41
progesteron
ductal elongation and side pranchion
42
secreting cells can also be based on
how cells secrete product
43
types of secretion
- merocrine
- apocrine
- holocrine
- cytocrine
44
merocrine secretion
cells secrete substances by exocytosis- fusion of vesical with apical membrane
- e.g. acinar (alveolar) and endocrine glands of pancreas
45
regulated secretion
- Secretory granules accumulate in large vesicles and are released by exocytosis upon stimulation
o Needs Calcium ions to work
46
constitutive secretion
- Secretory product is not concentrated into granules but packaged in small vesicles and continuously released to the cell surface
o Used to repopulate the plasma membrane with plasma proteins
47
apocrine
portion of the cell membrane and cytoplasm that contains excretion buds off
- e.g. lactating mammary gland, sweat glands in the axilla and externa genitalia
48
holocrine
entire cell disintegrates to excrete its substance
| - e.g. sebaceous glands of the skin and nose and tarsal glands in eyelid
49
cytocrine
cells are released as recreations e
50
example of cytocrine
spermatids in the seminiferous tubule
51
regulated merocrine secretion
- Uses ATP
1) Content of vesicle can be anything in the cell
2) Active secretion requires Ca2+ ions
3) Vesicle migrates to cell surface along microtubules
4) In presence of Ca2+ ions, membrane of vesicle fuses with plasma lemma
5) Cargo release into extracellular space
52
example of regulated merocrine secretion
Example: Insulin release
- Dependent on calcium influx for insulin to be secreted - is dependent on membrane depolarisation which allows for calcium channels to open to allow calcium to enter the cell
53
holocrine secretion example
Sebaceous gland
1. Secretory cell gradually fills up with secretory granules
2. Cell organelles degenerate
3. Cells die
4. Plasma membrane breaks and the contents (secretum) empties
5. Dead cells are replaced by mitotic division of the basal cells
54
definition of glycosylation of proteins
The covalent attachment of sugars by enzymes to p[routines and lipids to form glycoproteins and glycolipids
55
glycosylation occurs in the
golgi
56
role of glycosylation
- Avoid protein folding
- Prevent protein digestion by intracellular proteases
- Prevent lipid digestion by intracellular lipases
- Cell recognition (blood groups)
57
how many proteins undergo glycosylation
50%
58
how many disorders of glycosylation are known
40- rare and lethal
59
role of the golgi apparatus
1) Protein-containing vesicles from the ER transfer substances to the cis region of the Golgi apparatus
2) Golgi chemically modifies the proteins in its lumen e.g. by glycosylation
3) And targets them to the correct address
60
types of transport in and out of the cell (4)
exocytosis
endocytosis
phagocytosis
pinocytosis
61
exocytosis
• Secretion of molecules outside the cell via vesicle fusing to a membrane
62
endocytosis
• Engulfing of molecules inside the cell via vesicle formation
63
phagocytosis
* Process by which cells envelop or engulf other cells or particles
* Cells of the immune system: phagocytes (macrophages, dendritic, neutrophils, basophils, eosinophils)
64
pinocytosis
* Process by which liquid droplets are ingested by cells
| * Used by all cells esp SMC
65
transcytosis
movement across a membrane
66
types of transpeitheilal transport
paracellular
transcellular
Carrier protein
cell surge recpetors
67
paracellular
Molecules may move through aqueous channels in the intercellular junction (paracellular transport)
a. Amino acid for hormone production
68
transcellular
Through lipid membranes (transcellular)
| a. Steroid hormones (oestrogen, progesterone etc)
69
carrier protein
Transported by carrier proteins into or out of the cell
70
Molecules that are impermeable may bind to
cell surface receptors, be engulfed by the cell membrane (endocytosis) and then released inside the cell or expelled via exocytosis
a. Cholesterol transport (many drugs)
71
3 types of glandular control
humoral
neural
hormonal
72
humoral
exocrine and endocrine
e.g. substances in the blood may trigger release of hormone e.g. calcium
73
neural
only exocrine
e.g. neurones stimulating hormone secretion
74
hormonal
exocrine and endocrine
.g. the secretion of one hormone provides positive or negative feedback for the release of another hormone
75
example of gland that has neural communication
hypothalamus to the pituitary
76
Hypothalmo-hypophyseal portal system
- Neurons in the hypothalamus synthesising trophic hormone release them into the capillaries of the portal system
- The portal vessel carry the trophic hormones ( TSH) directly to the anterior pituitary
- Endocrine cells release their hormones into the second set of capillaries for distribution to the rest of the body e.g. T3/T4- thyroxine
o Provides negative feedback to Hypothalamus
