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Med 2024-2028 > TOB L4 > Flashcards

TOB L4 Flashcards

1
Q

Describe the classification of glands

A

DESTINATION OF SECRETION:
exocrine - via duct (into ductal system)
endocrine - ductless, into blood (directly into blood)

METHOD OF SECRETION
merocrine/eccrine (most glands) - producing a secretion that does not contain cellular componens and is discharged without major damage to secreting cell
apocrine (mammary glands)
holocrine - disintegration of entire glandular cell in releasing its products (sebaceous glands) - glands found in hair follicles, secrete sebum]

NATURE OF SECRETION
(serous/mucous)

ORGANISATION / STRUCTURE
simple or compound

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2
Q

Describe the process of merocrine secretion

A
  1. Contents released from golgi in a membrane-bounded secretory vesicle
  2. Fusion with vesicle + plasma membrane
  3. Release of non-membrane-bound contents into extracellular space
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3
Q

Histology showing how glands can be classified by structure

A

left: simple
right: compound

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4
Q

Describe how glands can be classified by structure

A
  1. SECRETORY PART: can be unicellular/mulkticellular
  2. ACINAR (small cavity in gland): COILED / TUBULAR / BRANCHED
  3. DUCT SYSTEM: simple gland (single duct)
    compound gland (branched ducts)
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5
Q

Give an example of a unicellular gland

A
  1. Goblet cells
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6
Q

Descibe the structure and function of goblet cells

A

Unicellular glands
Cells contain large golgi apparatus: add carbs to newly synthesised proteins to create mucin

Mucins released from cell, hydrated to produce mucus

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7
Q

How are mucins detected detected by PAS staining?

A

Mucins: hydrophillic, washed away during histological preperation, however, residual oligosachharides detected by PAS staining

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8
Q

Histology of goblet cells in upper respiratory epithelium

A
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9
Q

Histology of goblet cells in ileum

A
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10
Q

Describe the pathophysiology of cystic fibrosis

A

Autosomal recessive disorder (you need to inherit both genes from each parent)

due to mutation to CTFR gene which codes for cystic fibrosis transmembrane regulator (Cl- channel)

In CF, this channel is destroyed before reaching apical membrane

Decreases Cl- secretion

This increases intracellular Na+ and water reabsorption from lumen

Secreted mucus not adequately hydrated

So, its more difficult to move to the oropharynx for swallong

This leads to obstruction + infection

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11
Q

Define the term systemic

A

Affects entire system

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12
Q

Describe the effects of cystic fibrosis

A

Systemic:

LUNGS: Recurrent respiratory infections

PANCREAS: Blockage of ducts, leads to chronic pancreatits

GI tract: Reflux, difficulty passing stools (meconium ileus - inability to pass 1st faeces in newborns)

MALE REPRODUCTIVE SYSTEM: Failure of development of vas deferens leading to infertility

SKIN: salty sweat

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13
Q

State a method of confirming the diagnosis of cystic fibrosis

A

Testing for abnormally salty sweat
Absence of CTFR gene in apical membrane of epithelial cells
Poor absorptionof Cl- ions
This suppresses Na+ rearbsorption

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14
Q

How do we classify multicellular glands as simple?

A

DUCTS DO NOT BRANCH

(ducts - invaginations of epithelium, specialised for secretion)

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15
Q

State types and examples of simple multicellular glands

A
  1. SIMPLE TUBULAR: mucous glands of the colon (crypts of lieberkuhn)
  2. SIMPLE BRANCHED TUBULAR: glands of uterus + stomach
  3. SIMPLE COILED TUBULAR: SWEAT GLANDS
  4. SIMPLE ACINAR: SMALL MUCOUS GLANDS IN URETHRA
  5. SIMPLE BRANCHED ACINAR: SEBACEOUS GLANDS

on the diagram, pay attention to
- duct
- secretory portion

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16
Q

State an example of a simple tubular gland

A

Crypts of lieberkuhun

  1. Simple, straight, unbranched tubular glands
  2. Crypts lined with enterocytes + goblet cells
  3. Major function of colon is reabsorption of water + electrolytes + formation and passage of faeces
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17
Q

State an example of a simple coiled tubular gland

A

Sweat glands

  1. Secretory portions surrounded by contractile myoepithelial cells
  2. Contraction is under control of sympathetic nervous system
  3. Their contraction transports luminal contents towards ducts
  4. Ducts are lined with stratified cuboidal epithelium

Pay attention to adipose tissue (fat droplets) in histology, become more abundant with age

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18
Q

State an example of a simple branched acinar gland

A

Acinar - a group of berry like cells

Sebaceous glands

  1. Oily seubum released by lobes of acinar via single duct onto hair
  2. This is done by holocrine secretion, under control of androgens
  • Sebaceous glands found wherever you have hair
  • Found in skin, usually attached to hair follicles

HISTOLOGY IS SCALP

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19
Q

How do we classify complex glands

A

Ducts branch

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20
Q

State types of complex glands

A
  1. COMPUND TUBULAR: glands of brunner in duodenum (Brunner’s glands)
  2. COMPOUND ACINAR: Exocrine pancreas
  3. COMPOUND TUBULOACINAR: Salivary glands, mammary glands
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21
Q

Describe the duct system in a typical complex gland

A

What is the secreting portion? Acinus

What is the conducting portion? Duct

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22
Q

State an example of a complex acinar gland

A

EXOCRINE PANCREAS

The simple squamous epithelium of intercalated ducts penetrates acini in pancreas

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23
Q

Explain why cystic fifibrosis was previously known as fibrocystic disease of the pancreas

A
  1. Exocrine secretions contain too little water.
  2. They become thickened + block ducts
  3. The exocrine pancreas becomes painfully inflamed (pancreatitis) and fibrotic
  4. The gut recieves insufficient pancreatic digestive enztmes and malabsorption results
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24
Q

Why are cystic fibrosis patients often malnourished?

A

Gut recieves insufficient pancreatic digestive enzymes

Certain molecules such as proteins + fats cannot be broken down + absorbed into bloodstream

Symptoms of insufficient secretions of pancreatic digestive enzymes appear in the first year of life in 90% of cases

Insufficient lipase production results in faecal excretion of undigested fat, as diarrhea

The endocrine pancreas (islets of Langerhans) detoriarte more slowly, as no exocrine ducts

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25
Q

Describe the classification of glands by nature of secretion

A

MUCOUS GLANDS - secretions contain mucus, rich in mucins (highly glycosylated polypeptides). Stain poorly in H&E sections - mucous is water soluble, so stains lighter with H&E

SEROUS GLANDS - watery secretions (often containing enzymes). Eosinophilic (pink) in H&R sections
serous glands have granules - eosinphilic hence stain very strongly with H&E

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26
Q

State an example of a complex tuboloacinar gland

A

Major salivary glands

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27
Q

State the function and position of major salivary glands

A

Major / extrinsic salivary glands produce saliva
Lie outside oral cavity, empty their secretions into it

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28
Q

State the function and the position of the minor / intrinsic salivary glands

A

Example: Buccal glands

Scattered throughour oral cavity mucosa
Adjust output

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29
Q

State the major salivary glands

A
  1. Parotid
  2. Submandibular
  3. Sublingual
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30
Q

Describe the structrure and function of the parotid gland

A
  1. Has serous acini producing alpjha-amylase
  2. Ingestion of food stimulates release of saliva via parasympathetic innervation
  3. Strong sympathetic innervation leads to dry mouth (xerostomia)
  4. Parotid gland has striated ducts - important in Na+ reabsorption
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31
Q

Describe the structure and function of the submandibular gland

A
  1. Has serous acini producing alpjha-amylase
  2. In submandibular gland, the serous acini cells also produce lysozyme
  3. Lysozyme gives saliva its antimicrobial properties
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32
Q

Describe the structure and function of the sublingual gland

A

Contains mainly mucous acini

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33
Q

Describe the structure and function of the mammary glands

A

Type of tubuloacinar gland
Myoepithelial cells help secrete milk from acini
Contraction of myoepithelial cells under control of hormone oxytocin is experienced as “let down”
During lactation, after activation by prolactin, ducts become more developed

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34
Q

Histology showing difference between inactive and active mammary gland

A

We can see the ducts becoming more developed

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35
Q

Describe how mammary glands secrete

A

Via apocrine secretion

  1. Non membrane bound lipids push through the plasmalemma, covering dropleys with membrane and a thin layer of apical cytoplasm
  2. The membrane becomes transiently smaller and requires the addition of an extra membrane, to compensate for the lost membrane. This is done bia SER which synthesises lipids
  3. Other milk constituents including lactose, proteins and minerals are released by merocrine secretion

IT IS ONLY THE LIPIDS THAT ARE RELEASED VIA APOCRINE SECRETION

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36
Q

Describe the difference between apocrine and eccrine/,erocrine sweat glands in the body

A

Eccrine / merocrine sweat glands widely distrobuted
Aporcrine sweat glands develop at puberty in
-axillae
-areola of nipples
-geniral and perianal regions

37
Q

Describe which sweat glands are responsible for body odour

A

Apocrine sweat glands
Scent glands
The sweat secretion they produce is rich in protein which is easily metabolised by bacteria, giving the odour

38
Q

Describe the method of secretion used by apocrine sweat glands

A

Despite the name, apocrine sweat glands function via merocrine secretion
They are only called sweat glands to differentiate between normal ones and those that develop during puberty

39
Q

Give an example of a gland that is mixed (exocrine and endocrine)

A

Pancreas

40
Q

Describe the structure and function of the pancreas

A

Mixed exocrine / endocrine gland
Consists of clusters of glandular epithelium
99% acini
1% pancreatic islets

ACINI (EXOCRINE)
1. produce + secrete pancreatic juice, cells of serous acini contain zymogen granules
2. Acina cells produce
-peptidases
-lipases
-amylolytic enztnes
-nucleolytic enzymes

once these are synthesised,they leave acini via interalated ducts. Duct cells secrete watery bicarbonate rich fluid that hels flish enzymes through the ducts + neutralise any acid in duodenum

PANCREATIC ISLETS - ENDOCRINE

  1. Mostly located in tail region of pancreas
  2. Connected to each other via desmosomes + gap junctions forming bands of cells
    Pancreatic islets secrete hormones directly into the blood stream:
  3. Glucagon (produced by alpha cells) promotes gluconeogenesis and glycogenolysis
  4. Insulin (produced by beta cells) promotes glucose uptake by tissues
  5. Somatostatin (produced by delta cells)
  6. Pancreatic polypeptide
41
Q

State the function of zymogens

A

Inactive form of protein digesting enzyme (protease) of pancreas

Inactive so that it does not digest cells of pancreas itself

42
Q

Describe the contents of the pancreatic juice formed by acinar cells of pancreas

A

Acinar cells produce:

  1. Peptidases
  2. Lipases
  3. Amylolytic enzymes
  4. Nucleolytic enzymes
43
Q

Immunohistochemical detection of alpha and beta cells in pancreatic islet

A
44
Q

State an adaptation of the pancreas to allow efficient entry of pancreatic hormones into the blood

A

Pancreatic islets are surrounded by fenestrated capillaries

45
Q

Pancreatic histology

A
46
Q

Pancreatic histology

A
47
Q

Pancreatic histology

A

ACINI STAIN DARKER: due to serous secretions
ACINI ALWAYS HAVE DUCTS CLOSE: because xocrine (endocrine glands have no ducts)
ACINI HAVE LOTS OF GRANULES: contain zymogens
ACINI HAVE LOTS OF RER: lots of ribosomes for protein synthesis of zymogens

48
Q

Describe the contents of pancreatic juice

A

Pancreatic juice contains pancreatic proteases.

These include: trypsin, chymotrypsin.. Etc. These enzymes are released as zymogens

and are activated only once in the duodenum.

For example: trypsinogen is activated to trypsin by the intestinal brush border enteropeptidase.

The pancreatic amylases, lipases and nucleases are secreted in an active form but require presence of ions + bile activity

49
Q

Describe the structure and function of the thyroid gland

A

Endocrine gland
Located anterior (in front of) + inferior (below) the larynx

Composed of right + left lateral lobes connected by central isthmus

STRUCTURE:
1. consists of thyroid foillcles - thyroid functional unit
2. Wall of each thyroid follicle contains follicular cells
3. Basement membrane surrounds each follicles
4. Follicular cells produce colloid - clear viscous, thick, fills lumen of follicle
5. Parafollicular cells lie between follicles

50
Q

Describe what the colloid is made of

A

Tg - thyroglobulin
recursor to thyroid hormones (T3 and T4)

Tg facilitates assembly of thyroid hormones
T4 - Thyroxine
T3 - Triiodothyronine
This happens in thyroid follicular lumen

(THESE HORMONES REGULATE BMR)

51
Q

Anatomy of thyroid gland

A
52
Q

Histology of thyroid gland

A
53
Q

Histology of thyroid gland

A
54
Q

Histology of thyroid gland

A

Pay attention to parafollicular cells

55
Q

Describe the role of active thyrocytes

A

Thyrocytes - Thyroid Follicular Cells

  • Form cuboidal epithelium
  • That produces Thyroxine (T4)
  • That produces Triiodothyronine (T3)

These hormones regulate BMR (basal metabolic rate)

56
Q

State the role of parafollicular cells

A

C cells
Produce calcitonin
Slows bone turnover to reduce plamsa calcium

57
Q

Histology of simple cuboidal epithelium of the thyroid gland

A
58
Q

Describe how the shape of epithelium ranges when follicular cells are active and inactive

A

When follicular cells are inactive, the shape ranges from low cuboidal to squamous

When follicular are active, their shape ranges from cuboidal to low columnar

59
Q

State the role of cuboidal thyrocytes

A

Specialised epithelium
Release Tg into colloid

60
Q

What type of epithelium does the thyroid gland have?

A

Simple cuboidal

61
Q

Describe the control and synthesis of thyroid hormones

A

Thyroid stimulating hormone controls the release of thyroid hormones (TSH_
Produced in anterior pituitary

Thyrocytes (throid follicular cells) synthesise thyroglobulin (tyrosine rich glycoprotein) by the ER a and release it via exocytosis into the colloid

  1. Tyrosine residues within the thyroglobulin molecule undergo iodination at 1 or 2 positions
  2. An iodinated tyrosine residue is conjugated with a mono iodinated tyrosine resisdue to create pre-T3
  3. A di-iodinated tyrosine residue is conjugated with another di-iodinated tyrosine to create pre-T4
  4. The modofied thyroglobulin molecule is endocytosed following TSH stimulation then undergoes proteolytic cleavage in lyosomes to release mature T3 andT4 molecules from the polypeptide chain
  5. Thyroid hormones are released from the basal aspect of the cell by exocytosis and enter blood stream, where they are tranported in association with binding proteins (eg albumin)
62
Q

State the most abundant thyroid hormone

A

T4

63
Q

State the most stable thyroid hormone

A

T4

64
Q

State the most active thyroid hormone

A

T3

(although T3 and T4 bind to the same receptors)

65
Q

Describe how T4 can be converted to T3

A

In tissues
By removal of iodine molecule via deiodinase action
Removal of further iodine molecule creates inactive forms (rT3, T2)

66
Q

Describe the effect of high levels of thyroid hormone levels

A

Inhibit release of TSH in negative feedback loop

67
Q

Diagram showing synthesis of thyroid hormones

A
68
Q

Diagram of parathyroid gland

A
69
Q

Describe the location of the parathyroid glands

A

4 small glands
-Posterior surface of thyroid, also can be in chest
-Upper pair - superioir parathyroid gland
-Lower pair - inferioir parathyroid gland

70
Q

State two tyes of cells present in parathyroid gland

A

Chief cells -
Oxyphil cells - larger, stain differently, derivede from chiefc cells, INCREASE IN NUMBER WITH AGE, embedded in MATRIX or STOMA
Adipose cells (if adipose cells present, person older as adipose cells appear with age)
Lots of blood capillaries

71
Q

State where parathyroid hormone is produced

A

Chief cells / PRINCIPAL CELLS in parathyroid gland

PTH

72
Q

State the role of PTH

A

Stimulates bone resorption by osteoclasts
This raises blood calcium levels

(role of principal cells, as they secrete PTH)

73
Q

State the role of oxyphil cells

A

Function unclear

74
Q

Histology of cells in parathyroid gland

A
75
Q

Diagram of adrenal glands

A

Suprarenal glands

76
Q

Photomicrograph of the adrenal gland

A

Cortex has 3 layers, secretes corticosteroid hormones
Medulla secretes adrenaline + noradrenaline

HIGHLY VASCULARISED
ACTS AS ENDOCRINE GLAND

77
Q

Describe the position of the adrenal glands

A

Superior to each kidney in the retroperitoneal space
Embedded in perirenal adipose

78
Q

Describe showing the structure of the adrenal glands

A

Adrenal cortex made of:

  1. Zona glomerulosa
  2. Zona fasciculata
  3. Zona reticularis
79
Q

Diagram showing the structure of adrenal gland

A
80
Q

Diagram showing the structure of adrenal gland

A
81
Q

Describe the blood supply of the adrenal gland

A

Dual blood supply
Recieves arterial blood from medullary arteroles
Recieves venous blood from capillaries of cortex

82
Q

Describe an adaptation of the adrenal gland to maximise blood supply

A

Sinusoids - allow maximum exchange of macromolecules

83
Q

Histology of adrenal gland

A
84
Q

Describe the structure and funtion of the outer cortex of the adrenal gland

A

Outer fibrous capsule provides protection

Zona glomerulosa produces mineralcorticoids (e.g. aldosterone)

Zona fasiculata produces glucocorticoids such as cortisol

85
Q

Describe the structure and fucntion of the inner cortex and medulla of adrenal gland

A

Inner cortex: Zona reticularis - produces weak androgens

Medulla produces adrenaline and noradrenalune

86
Q

State the adrenal secretions and their role

A

Mineralcorticoids:
aldosterone regulates Na+ uptake by renal tubules

Glucocorticoids: Cortisol regulates carbohydrate metaboliosm

Gonadocorticoids: Weak androgens

Catecholamines: Stress response

87
Q

Describe the regulation of adrenal secretions

A
  1. ALDOSTERONE RELEASE:
    stimulated by Angiotensin II in response to low BP
  2. CORTISOL RELEASE: stimulated by adrenocorticotropic hormone (ACTH) released by anterior pituitary gland. That is stimulated by corticotropin releasing hormone (CRH) produced by hpothalamus in response to nervous stimulation (neuroendocrine control)
  3. ADRENALINE + NORADRENALINE: under nervous control, released from medullary chromaffin cells in resposne to sympathetic innervation. Promoye vasoconstriction, change in heart rate, elevated blood glucose levels
88
Q

State an example of neuroendocrine control

A

CORTISOL RELEASE: stimulated by adrenocorticotropic hormone (ACTH) released by anterior pituitary gland. That is stimulated by corticotropin releasing hormone (CRH) produced by hpothalamus in response to nervous stimulation

Med 2024-2028 (55 decks)

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