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MS 1 Unit VI Microscopic Anatomy > Unit VI- Exocrine Glands > Flashcards

Unit VI- Exocrine Glands Flashcards

1
Q

How do exocrine glands develop

A
  • induction by connective tissue
  • exocrine glands develop as invaginations of surface epithelium
  • exocrine glands retain a connection with the surface via ducts
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2
Q

Structural organization of glands

A
  • secretory portion: acinar or tubular
  • acinus (plural: acini) - is a berry like cluster of cells with a central lumen
  • conducting portion:ducts
  • in some glands, ducts also have secretory function
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3
Q

Classification of glands

A
  • single-cell glands
  • simple glands- single unbranched duct. Secretory portion can be branched or unbranced (sweat glands, sebaceous glands)
  • compound glands- multiple branched ducts. Secretory portion can be acinar, tubular, or tubuloacinar (salivary glands and exocrine pancreas)
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4
Q

Types of secretion

A
  • holocrine
  • apocrine
  • merocrine (called eccrine in sweat glands)
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5
Q

Holocrine

A
  • lysis of cells filled with secretory product

- example: sebaceous glands of skin

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6
Q

Apocrine

A
  • shedding of apical cell segment filled with secretory product
  • example: mammary glands
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7
Q

Merocrine

A
  • (called eccrine in sweat glands)
  • exocytosis of proteins or glycoproteins
  • examples: sweat glands, salivary glands, exocrine pancrease
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8
Q

Glandular epithelium in merocrine glands

A
  • serous cells
  • mucous cells
  • myoepithelial cells
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9
Q

Serous cells

A
  • stain well with H and E
  • secrete proteins
  • abundant RER and Golgi in the basal portion of the cell
  • secretory granules in the apical cytoplasm
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10
Q

Mucous cells

A
  • secrete mucin, made of glycoproteins rich in complex carbohydrates
  • mucins stain poorly with H and E but can be stained with periodic acid-Schiff (PAS) stain
  • abundant RER and Golgi in the basal portion of the cell
  • mucin filled secretory granules in the apical cytoplasm
  • upon secretion, mucin becomes mucus, a vicous, jelly-like protective lubricant
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11
Q

Myoepithelial cells

A
  • located within the same basal lamina as secretory or duct cells
  • possess long actomyosin-rich processes that surround the epithelial cells
  • contraction helps expel secretory product from the gland lumen
  • present in sweat, salivary, and mammary glands
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12
Q

Ion and fluid transport across glandular epithelia

A
  • ion channels and pumps. Example Na+/K+ ATPase
  • mitochondria provide source of energy
  • membrane specializations increase surface area
  • tight junctions seal off the apical surface from the basal surface
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13
Q

Unicellular glands

A

-goblet cells in the lining of the small intestine and in the respiratory epithelium of the trachea

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14
Q

Multicellular simple glands

A
  • sebaceous glands
  • eccrine sweat glands
  • apocrine sweat glands
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15
Q

Sebaceous glands

A

-simple branched acinar glands
-holocrine secretion
-associated with hair follicles
-basal layer of cells that proliferate and differentiate into sebocytes
-sebum composition: triglycerides, cholesterol, squalene, wax esters
Clinical correlation: origin of acne

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16
Q

Eccrine sweat glands

A
  • simple (coiled) tubular glands
  • stratified cuboidal epithelium in the duct and in the secretory portion
  • cholingeric fibers of sympathetic nervous system stimulate sweat secretion
  • pale (clear cells)- pyramidal to columnar in shape; located in periphery, resting on the basal lamina; produce watery component of sweat; contain abundant mitochondria; possess microvilli and intracellular canaliculli; have tight junctions
  • dark cells- pyramidal in shape, near lumen, secrete glycoproteins and proteins, including bactericidal peptides
  • myoepithelial cells: located within basal lamina; nucleus triangular or elongated; contain actomyosin-rich processes; contact to help expel the secretory product
  • sweat ducts:
  • epithelium stains darker than in secretory coli
  • re-absorb sodium and chloride
  • abundant Na+/K+ ATPase in the basal membrane
  • abundant mitochondria
  • tight junctions
17
Q

Apocrine sweat glands

A
  • located in the axillary, areolar and perineal regions
  • associated with hair shafts
  • simple coiled glands
  • the secretory coil is lined by simple cuboidal epithelium and has large lumen
  • merocrine secretion
  • secretory product may include pheromones
  • stimulated by adrenergic fibers of the sympathetic nervous system
18
Q

Function of saliva

A
  • moisture and lubrication
  • initiation of the digestion of carbohydrates: alpha- amylase
  • immune defense: lysozyme, lactoferrin and secretory IgA
  • secretion of calcium and phosphate to make acquired pellicle
19
Q

Structure and organization of salivary glands

A
  • connective tissue capsule
  • septa-extensions of the capsule that divide parenchyma into lobules
  • CT: capillary plexus that surrounds secretory and ductal components; nerves that control secretion: parasympathetic stimulation and sympathetic inhibition, lympocytes and plasma cells
  • lobules contain salivons: a secretory unit consisting of acini, intercalated ducts, and interlobular excretory ducts
  • acini drain into intercalated ducts
  • intercalated ducts drain into intralobular ducts
  • intralobular ducts drain into interlobular ducts located in the septa
20
Q

Acini in salivary glands

A

-types: mucous, serous, or mixed
Serous cells: pyramidal in shape, secrete proteins including sIgA
-Mucous cells:cuboidal to columnar in shape,secrete mucin
-myoepithelial cells (basket cells)- reside in basal lamina; possess long, branched contractile processes that prevent secretory protion distention and accelerate secretion; also present in ducts where they are spindle shaped and oriented along the duct length

21
Q

Intercalated ducts

A
  • small, 4-6 cells in circumference
  • cuboidal cells that lack secretory granules
  • connect the secretory portion to the intralobular duct
22
Q

Intralobular ducts

A
  • more that 6 cells in circumference
  • lined by simple columnar epithelium
  • basal striations: basal membrane infoldings that house mitochondria
  • active transport of ions: saliva contains 7x potassium, 3x bicarbonate, 1/10 sodium compared to blood plasma
  • mucous glands lack striated ducts
  • also secrete sIgA
23
Q

Interlobular ducts

A
  • large ducts located in septa

- lined with stratified cuboidal to columnar epithelium

24
Q

Mechanism of sIgA secretion

A
  • plasma cells secrete dimeric IgA
  • serous cells and intralobular duct cells produce IgA receptor
  • IgA receptor mediates transcytosis of IgA into gland lumen
  • proteolysis of receptor produces sIgA, the IgA in complex with receptor fragment called secretory components
25
Q

Submandibular gland

A
  • compound tubuloacinar gland
  • serous and mucous acini
  • mixed acini: serous demilunes
  • serous cells secrete proteins including lysozyme
  • some intralobular ducts are striated
26
Q

Parotid gland

A
  • compound acinar gland
  • serous acini
  • secretes alpha-amylase and other proteins
  • intercalated ducts are long
  • intralobular ducts are striated
  • a diagnostic feature: the presence of abundant adipose tissue
27
Q

Sublingual gland

A
  • compound tubuloacinar gland
  • primary mucous acini
  • some mixed acini with serous demilunes
  • intralobular ducts are not striated
28
Q

Structure and function of exocrine pancreas

A
  • compund acinar gland (similar to parotid)
  • lobules separated by connective tissue septa
  • septa contain blood vessels, lymphatics, nerves, and ducts
  • secretory product contains: digestive proenzymes including proteases, lipases, nucleases, and amylolytic enzymes
  • pancreatic enzymes are inactive and are activated by enterokinase cleavage in the duodenum. Pancreas also produces protease inhibitors
29
Q

Serous acini of exocrine pancreas

A
  • polarized serous cells surround small lumen
  • abundant Golgi and RER
  • zymogenic granules in the apical half of the cells (toward lumens)
  • lack of myoepithelial cells
  • secretion is stimulated by cholecystokinin, a hormone produced by enteroendocrine cells in duodenum
30
Q

Intercalated ducts of exocrine pancreas

A
  • protrude into acini as centroacinar cells
  • lack secretory granules
  • produce bicarbonate
  • secretin, another hormone produced by enteroendocrine cells in duodenum, stimulates bicarbonate release
31
Q

Intralobular ducts of exocrine pancreas

A
  • lack striations

- also secrete bicarbonate-rich fluid

32
Q

Interlobular ducts of exocrine pancreas

A
  • low columnar epithelium

- also secrete bicarbonate rich fluid

33
Q

Endocrine pancreas

A
  • the endocrine portion of the pancreas is represented by the islets of Langerhands
  • this is a diagnostic feature of the pancreas
34
Q

Medical applications

A
  • adenocarcinomas, the malignant tumors of glandular epithelia, are some of the most common tumors in adults
  • reduced function of salivary glands due to disease or radiotherapy
  • necrotizing pancreatitis

MS 1 Unit VI Microscopic Anatomy (5 decks)

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