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_Sem 1. BL NOTES > BL L9 > Flashcards

BL L9 Flashcards

1
Q

Define gland

A

An epithelial cell or an aggregate of epithelial cells that are SPECIALISED FOR THE SECRETION OF A SUBSTANCE

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2
Q

Define secretion

A

The production and release of materials by a cell or aggregate of cells

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3
Q

In one sentence, what is the major role of glands

A

Glands regulate human physiology to a large extent by receiving a stimulus for the brain, but also from circulating levels of chemicals (e.g. from blood) and from neighbouring cells

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4
Q

Name two ways glands can be classed?

A
  • Structure

- How the release their products

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5
Q

Name two types of gland structure

A
  • Endocrine (ductless)

- Exocrine (ducted) (Ex - ‘got an exit’)

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6
Q

Endocrine glands (where do they secrete, what do they secrete, how far does this secretion have an impact on?)

A 
DUCTLESS
- These glands secrete directly into blood flowing through them
- Secreting into the blood lets the secretion function at distant parts of the body. 
- Secrete hormones 
Examples:
• Pituitary gland 
• Thyroid gland
• Parathyroid gland
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7
Q

Pituitary gland: Location, structure, what each part does

A

• Pituitary Gland (of the hypothalamus): beneath (inferior to) the hypothalamus in the brain.

Anterior (front part) pituitary gland: produces hormones (ACTH, LH, FSH, TSH) that regulate most of the glands of the endocrine system; prolactin: stimulates milk production in mothers; somatotrophin: A hormone which regulates the growth of the body and tissues

Posterior (rear part) pituitary: produces vasopressin (ADH or anti-diuretic hormone) that prevent water loss from kidneys. Oxytocin, which signals uterus for delivery in pregnant women at the end of gestation and ejection of milk during breast feeding.

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8
Q

What does the anterior part of the pituitary gland produce?

A

ACTH, LH, FSH, TSH, prolactin, somatotrophin

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9
Q

What does the posterior part of the pituitary gland produce?

A

Vasopressin (ADH), oxytocin

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10
Q

Thyroid gland

A

Endocrine gland
Produces thyroid hormones T3 & T4 that control metabolism; calcitonin, involved in calcium homeostasis

NEED TO LEARN NAMES OF ALL THE HORMONE SHORTENINGS

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11
Q

Parathyroid gland

A

Endocrine gland

Produces parathyroid hormone, calcium homeostasis

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12
Q

Do all the epithelial cells secrete hormones in endocrine glands?

A

Yes they do, all epithelial cells secrete the hormones in the gland

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13
Q

Exocrine gland (where do the secretions go? What is secreted? Examples)

A 
DUCTED 
- These glands secrete into a location or region of the body through a duct, and their secretions are mostly enzymes or lubricants.
Examples:
• Salivary gland
• Pancreas
• Mammary
• Sweat glands
• Sebaceous gland
• Lachrymal glands
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14
Q

Salivary glands

A

Exocrine gland

In the buccal cavity secrete saliva. Saliva has many functions including partial digestion of food and lubrication

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15
Q

Pancreas

A

Exocrine gland

Secretes enzymes: amylase, trypsin, and lipase. These enzymes digest carbohydrates, proteins and fats, respectively

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16
Q

Mammary gland

A

Exocrine gland

Produces colostrum and milk in response to prolactin and oxytocin (hormones) to nourish neonates

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17
Q

Sweat gland

A

Exocrine gland

Secrete sweat, which acts to regulate body temperature and also excretion

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18
Q

Sabaceous gland

A

Exocrine gland

Secretes sebum onto the skin and in the ear (contributes to earwax) to protect these tissues from pathogens

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19
Q

Lachrymal gland

A

Exocrine gland

In eye secrete water to moisten the eye, also produce lysozyme (an enzyme to attack bacteria).

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20
Q

Explain how glands are made

A

(refer to pic in notes)
1. The cells in the connective tissue layer (called fibroblasts) make a growth factor called FGF (fibroblast growth factor)
2. FGF stimulates the epithelial cells that have a receptor to proliferate (‘proliferation of daughter cells’). As they proliferate, it produces an enzyme that degrades the extracellular matrix in the connective tissue layer.
3.Epithelial cells invade space created and grow into a ball of cells
WHAT HAPPENS TO EXOCRINE GLANDS:
— Exocrine gland: Central cells die off to produce duct
(canalicularisation). There are two types of cells in this gland: ductal cells (don’t secrete anything) and cells at the apex at the end of the gland which do secrete.
WHAT HAPPENS TO ENDOCRINE GLANDS:
— Endocrine gland: The epithelial produce angiogenic factors (growth factors) that stimulate blood vessel growth in and around the epithelial cells. At the same time, the link to connecting mother to daughter cells breaks off through apoptosis, therefore a duct isn’t formed. Instead, we get an aggregation of epithelial cells with blood vessels around it.

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21
Q

What are the two types of cells in exocrine gland?

A
  • Ductal cells (do not secrete anything)

- Apex cells (secretory portion)

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22
Q

How does branching occur? e.g. lung

A
  • Fibroblast cells release more FGF
  • Epithelial cells move towards this signal
    Two fates:
    1. Tube elongation: Growth factor 1 is active, growth factor 2 is inactive
    2. Tube branching: Growth factors 1 is inactive, growth factor 2 is active. With branching, growth factor 1 causes elongation, it then becomes inactive and growth factor 2 becomes active. Growth factor 2 causes the tubes to then branch. Then growth factor 2 turns off and growth factor 1 turns back on, causing the elongation of both branches, etc.
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23
Q

What is an acinar gland?

A

Alveoli gland

24
Q

What is a simple duct structure?

A

1 ‘main’ duct in all of these

25
Q

What is a compound duct structure?

A

Multiple ducts in these

26
Q

What are intercalating ducts?

A

Joining the acinar together (connect different acini)

27
Q

What are interlobular ducts?

A

Connecting different lobules

28
Q

What is the acinus

A

Acinus makes and releases secretions

Acinus means ‘berry’ - the sac cavity in the gland

29
Q

‘Different stages in the duct’

A

Acinus - makes and releases secretions
Myoepthelium - ‘squeezes cells to release more secretions’
Intercalating duct - connect different acini
Striated duct - keeps ductal system open and re-absorb Na+ and K+ ions
Excretory duct - sometimes has surround smooth muscle cells
Main collecting duct - collates all the secretions

30
Q

Talk about all the different shapes of gland ducts

A

TUBULAR SECRETORY STRUCTURE:

  • Simple tubular
  • Simple branched tubular
  • Compound tubular
31
Q

Different shapes of gland ducts

A

TUBULAR SECRETORY STRUCTURE:

  • Simple tubular
  • Simple branched tubular
  • Simple coiled tubular
  • Compound tubular

ALVEOLAR SECRETORY STRUCTURE:

  • Simple alveolar (acinar)
  • Simple branched alveolar (acinar)
  • Compound alveolar (acinar)
  • Compound tubuloalveolar (tubuloacinar)
32
Q

Salivary gland - Example (type of gland, two types of fluid production, 3 types of machanism/types or secretions available)

A

Type of gland: Compound alveolar

Two types of fluid production:

  • Mucous acinus - like goblet cells, produce mucus, producing enzymes and lubricant
  • Serous acinus - produces serum like substance, liquid bit of protein, like purple on H+E stain

3 types of mechanism/types of secretions available:

  • Mucuous only
  • Serous only
  • Mixture of both
33
Q

Talk about mammary gland and development

A
  • Develop starts in an embryo
  • Development then stops until puberty
  • At puberty, estrogen and progesterone produced by the ovaries restart breast development (gland containing to elongate and bud)
34
Q

Blockage of the glandular ducts

A

Secretion from multicellular exocrine glands may become obstructred by a ‘stone’

35
Q

Name the ‘mode of secretion’

A 
('MAHC')
Merocrine gland 
Apocrine gland 
Holocrine gland 
Cytocrine gland
36
Q

Merocrine secretion

A

Merocrine secretion is the fusion of vesicles with apical membrane, form of exocytosis

  • Membrane bounded compartment approaches cell surface
  • If fuses with plasma membrane
  • Its contents are in continuity with extracellular space and so dispersed by diffusion
  • Plasma membrane transiently larger
37
Q

Merocrine secretion - 1st pathway - Constitutive Secretion

A

Constitutive Secretion: The secretory product is packaged into small vesicles and CONTINUOUSLY released to the cell surface.
- Proteins being made by the RER are being packed into the vesicles. Some of the proteins will be inside of the vesicle, some will be on the membrane of the vesicles formed. SOME HAVE TARGET PROTEINS ON THEIR SURFACE Some have target proteins that send them off to the plasma membrane. When it gets to the plasma membrane, it fuses with it and repopulates the plasma membrane with some proteins, the material that the vesicle is carrying is released into the extracellular space. Used mainly to repopulate the plasma membrane with plasma proteins.

38
Q

Merocrine secretion - 2nd pathway - Regulated Secretion

A

Active process – uses energy

  1. Contents of vesicle (cargo) can be anything within the cell
  2. Active secretion requires specific signal (Ca2+ ions)
  3. Vesicle migrates to cell surface along microtubules
  4. In presence of Ca2+ ions, membrane of vesicle fuses with plasmalemma
  5. Cargo released to extracellular space
39
Q

Clinically relevant example of Merocrine gland - beta cells in the pancreas

A

Merocrine secretion - beta cell in the pancreas releasing insulin

  • Influx of Ca2+ ions causes the vesicles that contain insulin to fuse with the membrane and release insulin through exocytosis
  • Clinical link: Sulphonylurea given to patients to increase their insulin concentrations, the sulphonylurea binds to sulphonylurea receptor (the sulphonylurea receptor is attached to ATP-sensitive K+ channel), this closes the K+ channel, increasing K+ concentration in the cell, causing influx of Ca2+, this causes exocytosis of cells, releasing insulin.
40
Q

Apocrine gland

A

Partial loss of the apical part of the cytoplasm. Secretory product accumulates at the apical surface, it becomes unstable and pinches off. The cell then releases it’s secretory product, the cell then repairs itself and continues releasing it’s product in the same way.

41
Q

Example of apocrine gland - Mammary gland

A

Neonatal period:
Only FATS are secreted by apocrine secretion (signet fragment). The VESICLE GETS BIGGER AND BIGGER, the apical surface then become unstable and break off. When break off on their own, just become a fat droplet, it takes the cytoplasm with them, they are called a signet fragment.
Milk proteins made in RER and on free ribosomes are packed into vesicles produced by the Golgi apparatus - released by merocrine secretion
During lactation: both fats and proteins are released by apocrine secretion

42
Q

Halocrine gland

A

Complete loss of cytoplasm or cell (usually complete loss of the cell).
Cells ACCUMULATES THE SECRETORY PRODUCT, the entire cell RUPTURES to RELEASE THE PRODUCT. The ruptured cells are replaced by other epithelial cells through cell division

43
Q

Example of Halocrine secretion - Sebaceous gland

A
  1. The secretory cell gradually fills up with secretory granules
  2. The cell organelles degenerate
  3. The cells die
  4. The plasma membrane breaks and the
    contents (secretum) empties
  5. Dead cells are replaced by mitotic division of
    the basal cells
44
Q

Cytocrine gland

A

Cells are released as a secretion, e.g. only one example - spermatozae in the testes

45
Q

Secretion - Golgi apparatus

A

Proteins come in from ER -> processed in the golgi apparatus -> either constitutive pathway or regulated secretory pathway (vesicles will then go out of the cell or to other parts of the cell)

46
Q

Golgi apparatus - Function

A
  • Transport through the Golgi apparatus cisterna
  • Packaging of sorted contents through condensation
  • Glycoslyation: Adding sugars to proteins and lipids
47
Q

Glycosylation - more depth

A

Definition: The covalent attachment of sugars by enzymes to proteins and lipids to form glycoproteins and glycolipids.
Occurs in ER and golgi apparatus.

48
Q

Role of glycosylation

A
  1. To aid protein folding
  2. Prevents protein digestion by intracellular proteases
  3. Prevents lipid digestion by intracellular lipases
  4. Cell recognition (blood groups)
  5. Role on cell to extracellular matrix attachment
49
Q

Difference between glycosylation and glycation

A

Glycation: the same as glycosylation but in the absence of enzymes

50
Q

Define exocytosis and endocytosis

A

Exocytosis: secretion of molecules outside the cell via a vesicle fusing to a membrane
Endocytosis: Engulfing of molecules inside the cell via vesicle formation

51
Q

What are the three mechanisms of endocytosis

A
  1. Phocytosis
  2. Pinocytosis
    (3. Receptor mediated endocytosis)
52
Q

Phagocytosis

A 
Process by which cells
(phagocytes), envelop or engulf other
cells or particles
mainly used by cells of the immune system,
i.e. macrophages, dendritic cells,
neutrophils, basophils and eosinophils
53
Q

Pinocytosis

A

Process in which liquid
droplets are ingested by cells
used by all cells, especially smooth muscle
cells

54
Q

What is transepithelial transport? (transcytosis)

A

Getting things across the cell membrane

55
Q

Explain the 4 types of transepithelial transport

A

A. Molecules may move (passive diffuse + be filtered
with water) through aqueous channels in the
intercellular junction (paracellular transport)
B. or through lipid cell membranes (transcellular
transport)
C. Molecules with the appropriate characteristics
may be transported by carrier proteins into or out of
the cells or by a counter-transport process.
D. Molecules that are impermeable may also bind to
cell surface receptors, be engulfed by the cell
membrane (endocytosis) and then released inside
the cell or expelled via membrane-limited vesicles
out of the cell and into the extracellular space
(exocytosis)

56
Q

Name the three types of glandular control (the stimulus for the gland to release it’s substance)

A
  1. Humoral stimulus (changing level of substance in plasma -> endocrine gland -> target cell -> action)
  2. Neural stimulus (nervous system -> endocrine gland -> target cells -> action)
  3. Hormonal stimulus (hypothalamus -> pitituary gland -> peripheral endocrine gland -> target cell -> action)
57
Q

Neurocrine communication

A

e.g. the hypothalamus to the pituitary. The secretory cell is not epithelial - it is actually a nerve cell. The neurone releases something into the blood, which will then travel around the blood to a target cell which has a receptor for this particular neurotransmitter. Cells without neurotransmitter won’t respond.

_Sem 1. BL NOTES (21 decks)

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