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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
Describe the classification of glands by nature of secretion
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
26
State an example of a complex tuboloacinar gland
Major salivary glands
27
State the function and position of major salivary glands
Major / extrinsic salivary glands produce saliva Lie outside oral cavity, empty their secretions into it
28
State the function and the position of the minor / intrinsic salivary glands
Example: Buccal glands Scattered throughour oral cavity mucosa Adjust output
29
State the major salivary glands
1. Parotid 2. Submandibular 3. Sublingual
30
Describe the structrure and function of the parotid gland
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
31
Describe the structure and function of the submandibular gland
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
32
Describe the structure and function of the sublingual gland
Contains mainly mucous acini
33
Describe the structure and function of the mammary glands
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
34
Histology showing difference between inactive and active mammary gland
We can see the ducts becoming more developed
35
Describe how mammary glands secrete
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
36
Describe the difference between apocrine and eccrine/,erocrine sweat glands in the body
Eccrine / merocrine sweat glands widely distrobuted Aporcrine sweat glands develop at puberty in -axillae -areola of nipples -geniral and perianal regions
37
Describe which sweat glands are responsible for body odour
Apocrine sweat glands Scent glands The sweat secretion they produce is rich in protein which is easily metabolised by bacteria, giving the odour
38
Describe the method of secretion used by apocrine sweat glands
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
Give an example of a gland that is mixed (exocrine and endocrine)
Pancreas
40
Describe the structure and function of the pancreas
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: 1. Glucagon (produced by alpha cells) promotes gluconeogenesis and glycogenolysis 2. Insulin (produced by beta cells) promotes glucose uptake by tissues 3. Somatostatin (produced by delta cells) 4. Pancreatic polypeptide
41
State the function of zymogens
Inactive form of protein digesting enzyme (protease) of pancreas Inactive so that it does not digest cells of pancreas itself
42
Describe the contents of the pancreatic juice formed by acinar cells of pancreas
Acinar cells produce: 1. Peptidases 2. Lipases 3. Amylolytic enzymes 4. Nucleolytic enzymes
43
Immunohistochemical detection of alpha and beta cells in pancreatic islet
44
State an adaptation of the pancreas to allow efficient entry of pancreatic hormones into the blood
Pancreatic islets are surrounded by fenestrated capillaries
45
Pancreatic histology
46
Pancreatic histology
47
Pancreatic histology
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
Describe the contents of pancreatic juice
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
Describe the structure and function of the thyroid gland
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
Describe what the colloid is made of
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
Anatomy of thyroid gland
52
Histology of thyroid gland
53
Histology of thyroid gland
54
Histology of thyroid gland
Pay attention to parafollicular cells
55
Describe the role of active thyrocytes
Thyrocytes - Thyroid Follicular Cells - Form cuboidal epithelium - That produces Thyroxine (T4) - That produces Triiodothyronine (T3) These hormones regulate BMR (basal metabolic rate)
56
State the role of parafollicular cells
C cells Produce calcitonin Slows bone turnover to reduce plamsa calcium
57
Histology of simple cuboidal epithelium of the thyroid gland
58
Describe how the shape of epithelium ranges when follicular cells are active and inactive
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
State the role of cuboidal thyrocytes
Specialised epithelium Release Tg into colloid
60
What type of epithelium does the thyroid gland have?
Simple cuboidal
61
Describe the control and synthesis of thyroid hormones
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
State the most abundant thyroid hormone
T4
63
State the most stable thyroid hormone
T4
64
State the most active thyroid hormone
T3 (although T3 and T4 bind to the same receptors)
65
Describe how T4 can be converted to T3
In tissues By removal of iodine molecule via deiodinase action Removal of further iodine molecule creates inactive forms (rT3, T2)
66
Describe the effect of high levels of thyroid hormone levels
Inhibit release of TSH in negative feedback loop
67
Diagram showing synthesis of thyroid hormones
68
Diagram of parathyroid gland
69
Describe the location of the parathyroid glands
4 small glands -Posterior surface of thyroid, also can be in chest -Upper pair - superioir parathyroid gland -Lower pair - inferioir parathyroid gland
70
State two tyes of cells present in parathyroid gland
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
State where parathyroid hormone is produced
Chief cells / PRINCIPAL CELLS in parathyroid gland PTH
72
State the role of PTH
Stimulates bone resorption by osteoclasts This raises blood calcium levels (role of principal cells, as they secrete PTH)
73
State the role of oxyphil cells
Function unclear
74
Histology of cells in parathyroid gland
75
Diagram of adrenal glands
Suprarenal glands
76
Photomicrograph of the adrenal gland
Cortex has 3 layers, secretes corticosteroid hormones Medulla secretes adrenaline + noradrenaline HIGHLY VASCULARISED ACTS AS ENDOCRINE GLAND
77
Describe the position of the adrenal glands
Superior to each kidney in the retroperitoneal space Embedded in perirenal adipose
78
Describe showing the structure of the adrenal glands
Adrenal cortex made of: 1. Zona glomerulosa 2. Zona fasciculata 3. Zona reticularis
79
Diagram showing the structure of adrenal gland
80
Diagram showing the structure of adrenal gland
81
Describe the blood supply of the adrenal gland
Dual blood supply Recieves arterial blood from medullary arteroles Recieves venous blood from capillaries of cortex
82
Describe an adaptation of the adrenal gland to maximise blood supply
Sinusoids - allow maximum exchange of macromolecules
83
Histology of adrenal gland
84
Describe the structure and funtion of the outer cortex of the adrenal gland
Outer fibrous capsule provides protection Zona glomerulosa produces mineralcorticoids (e.g. aldosterone) Zona fasiculata produces glucocorticoids such as cortisol
85
Describe the structure and fucntion of the inner cortex and medulla of adrenal gland
Inner cortex: Zona reticularis - produces weak androgens Medulla produces adrenaline and noradrenalune
86
State the adrenal secretions and their role
Mineralcorticoids: aldosterone regulates Na+ uptake by renal tubules Glucocorticoids: Cortisol regulates carbohydrate metaboliosm Gonadocorticoids: Weak androgens Catecholamines: Stress response
87
Describe the regulation of adrenal secretions
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
State an example of neuroendocrine control
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 (56 decks)

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