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COT - Exam 2 > 11.3 - Branching Morphogenesis > Flashcards

11.3 - Branching Morphogenesis Flashcards

1
Q

What are the 4 ways glands can be classified based on

A

1) location
2) mode of secretion (i.e. how they secrete)
3) Type of secretion (i.e. what they secrete)
4) Shape

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2
Q

Describe glandular classification based on location

A
  • ex submucosal gland –> seen in extra pulmonary bronchus - in the submucosal layer
    (can also be classified based on type of secretion - i.e. mucus/serous submucosa glands)
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3
Q

Describe glandular classifications based on mode of secretion –> what are the different modes of secretion possible that could be used for classification of glands

A
  • Merocrine - product in granules
  • apocrine - lipid product
  • holocrine - cell lyse to secrete contents
  • exocrine - produce released into lumen
  • endocrine - product released into CT/blood through basal surface
  • constitutive - product released as it is produced
  • regulated - product released in controlled fashion
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4
Q

Describe merocrine secretion

A
  • product contained in granules
  • mostly protein products
  • can be serous or muscus products
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5
Q

Describe apocrine secretion

A
  • lipid product

- as product leaves it takes a portion of cell membrane with it

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6
Q

Describe holocrine secretion

A
  • cells lyse to secrete contents
  • for glands that rise from multilayered epithelium
  • see piqnotic nuclei before product is released (apoptotic)
    ex. sebaceous glands = stratified holocrine glands
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7
Q

Describe exocrine secretion

A
  • product released into lumen - through apical surface

- how you most commonly see merocrine, apocrine, holocrine type secretions in this category

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8
Q

Describe endocrine secretion

A
  • product released into CT or blood

- release through basal surface or basolateral surface

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9
Q

Describe constitutive secretion

A
  • product is release as it is produced
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10
Q

Describe regulated secretion

A
  • product released in controlled fashion

- many glands was see are this type

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11
Q

Describe glandular classification based on type of secretion

A

1) serous = watery secretion (i.e. most proteins are secreted this way
2) Mucus = glycoprotein secretion
- differences between 1 & 2 are often apparent in LM
3) Seromucus = mixed products, usually in adjacent cells –> serous cells in mixed seromucus cells tend to squeeze out and form half mood shape around gland - called serous demilune (during preparation)

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12
Q

Describe glandular classification based on Shape

A

of cells
1) Unicellular
2) Multicellular
Shape of Pathway from gland to lumen
1) Simple - straight forward connection to lumen
2) Branched - multiple diversions to path
3) Compound - (most of larger glands are this) complicated glands involving ducts (with have distinct epithelium from the glandular epithelium)
Gland Shape
1) Tubular = test-tube-like
2) Acinar = raspberry(grape-bunch)-like appearance - have exceedingly tiny lumens
3) Alveolar = large lumen but circular profile of gland (ex. = apocrine sweat glands)

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13
Q

What are the examples of gland shape given in the video

A
  • Simple Tubular
  • Simple coiled tubular (eccrine sweat glands)
  • Simple branched tubular (gastric glands)
  • Simple Acinar
  • Compound tubular (Brunner’s Glands)
  • Compound Acinar (Exocrine pancreas)
  • Compound tubuloacinar (salivary glands)
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14
Q

Describe the digestive glands of the oral cavity

A
  • All have discrete lobular organization
  • all have acinar morphology
  • all are paired
  • differ in type of secretion
  • formed by process of branching morphogenesis
  • 3 salivary glands
    1) Parotid glands
    2) Submandibular glands
    3) Sublingular Glands
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15
Q

Describe the parotid glands

A
  • nuclei are basal
  • zymogen granules
  • located over temporal mandibular joint (TMJ)
  • relatively long/large ducts
  • paired glands
  • pure serous secretion
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16
Q

Describe the submandibular glands

A
  • located around/beneath/lateral to mandible bone
  • relatively long/large ducts
  • paired glands
  • mixed seromucus secretion (90% serous/10% mucus)
  • look for serous demilune here
17
Q

Describe the sublingular glands

A
  • under the tongue
  • relatively short ducts
  • paired glands
  • mixed seromucus secretion (50/50)
  • look for serous demilune here
18
Q

Describe the organization of the salivary glands

A

A) Excretory Duct
B) interlobular duct
C) intralobular duct
D) striated ducts - have basal striations (see as fine lines) - are larger ducts with tall columnar cells
E) Intercalated ducts - very little cells more toward cuboidal shape - are farther out in branch
F) Secretory acini - predominate in the histological section

19
Q

Describe the Exocrine pancreas

A
  • Formed by branching morphogenesis

- pure serous secretion

20
Q

Describe the organization of the Exocrine pancreas

A

A) Excretory duct (Wirsung, Santorini)
B) Interlobular ducts - 2 majro lobes of pancreas
C) Intralobular ducts
D) intercalated ducts (bicarbonate secretion) - distinct lumen - functionally important in pancreas
E) Centroacinar cells (bicarbonate secretion) - morphologically like a duct (intercalated ducts) - but sits in lumen of acinus
F) Secretory Acini (Zymogen secretion)

21
Q

Describe the endocrine pancreas

A
  • Pancreatic Islets (of langerhans)
  • clumps of endocrine cells
  • no duct
  • no obvious lumen
  • capillaries are important feature of this + all endocrine glands because they take product away
22
Q

Serous gland

A

= gland that secretes a water-absed substance

23
Q

mucous gland

A

= gland that secretes mucus (i.e. glycoprotein-based substance)

24
Q

seromucous gland

A

= gland secretes both types of product (serous + mucous) - usually via different cells

25
Q

Multicelllular gland

A

B) = may be simple tubular invaginations of epithelial surface

A) may be branched structures
A) branched glands
= considered compound if they have branched ducts = tubes specialized not to secrete but rather to convert product to the organ’s lumen
- unbrancehd duct might be present in a simple gland (e.x. eccrine sweat glands (simpler coiled tubular et have specialized ductal cells

26
Q

Glands may classed by the shape of the secretory unit:

A

1) tubular
2) alveolar
= pit like, (like the bottom of a test tube)
3) tubulo-alveolar (mixture of both)
4) acinar
- like a raspberry or blackberry

  • -> tubular and laveolar gland have visible lumen
  • acinar glands usually do not
27
Q

Serous demilunes

A

= in a mixed acinar gland

- serous cells form this structure around the outsid of the acinus –> artifact due to expansion of adjacent mucus cells

28
Q

Excretory duct

A

= in large compound glands

- the largest proximal duct

29
Q

Other ducts

A

a) striated ducts - with basal striations

b) intercalated ducts

30
Q

Centroacinar cell

A

= ducts of the pancreas end is this specialized cell type

31
Q

lactiferous ducts

A

= ducts in the breast

32
Q

3) specialized regions of lactiferous ducts

A

1 - intralobular ducts
2 - interlobular ducts
3 - lactiferous sinus near the nipple

33
Q

Overview of the lung formation via branching morphogenesis

A

1) airways of respiratory system arise form endodermal bud
- growth to form 17-18 branches in the adult
- among the branches respecification happens only once
- growing cells transition from a conducting (further respiratory epithelium) to a respiratory (future alveolar epithelium) morphology
- respiratory branches form late in embryonic life = 5th month - must happen for life outside the womb

34
Q

Describe the 5 stages of trachea and lung development as an outgrowth of the esophageal portion of the endodermal gut tube

A

1) Embryonic
- lung bud arises from esophagus
- 1st several generations of bronchial branching occur
- tertiary bronchi (third branching) define the basic lobar outline of the adult lung:
- 3 lobes on right
- 2 lobes on the left
2) Pseudoglandular
- embryonic weeks 5-17
- bronchial branching up to 21 generations continues
- only one epithelial type i present
- bronchi fill the space afforded by pleural cavity –> which gives the lung a mesodermal lining (the future visceral peritoneum
- look similar to a gland at this stage
3) Canalicular Stage
- embryonic weeks 16-24
- epithelial cells of the distal ends of the bronchi (where contact capillaries) specialize into a flattened shape
- these cells continue to proliferate around the proliferating capillary bed –> forming alveolar sacs
- production of surfactant - begins during this stage
4) Saccular stage
- embryonic weeks 24-34
- alveolar sacs gain a mature lung-air interface
- are capable of high-efficiency gas exchange
5) alveolar stage
- beginning at week 34 of gestation –> end 2-4 years postnatal
- marked by increase in number of functional alveoli

35
Q

Major glands developed from branching morphogenesis

A
  • most major glands arise from an epithelial bud
  • first one or several branches usually form ducts
  • final branches from the secretory portions of the glands
  • examples of these
    1) three major salivary glands
    2) pancreas
    3) breast
36
Q

Kidney branching morphogenesis development

A
  • embryonic duct –> mesonephric duct forms retroperitoneally from fetal mesenchymal tissue
  • this duct contributes to the structure of the uretrha, bladder, and ureter in the adult
  • branches of the duct invade the mesenchymaltissue of the fetal kidney and become the calyces, collecting ducts, and collecting tubulaes of the kidney
  • each adult kidney lobe arises foam distinct branch of the fetal mesonephric duct –> those these lobes grout together in the adult kidney
37
Q

Uniqueness of the kidney from a branching morphogenesis standpoint:

A
  • major epithelial structure in the kidney = the nephron
  • -> does not arises from branching morphogenesis
  • each nephron is induced to form at the terminus of branching mesonephric tissue
  • nephrons are induced to form from fetal CT and elaborate long morphologically complex tubule that eventually connects its lumen wight eh mesonephrics lumen
  • the fetal CT that surrounds the mesonephric buds in the kidney - the metanephros = the structure that gives rise to a nephron is a metanephric bud

COT - Exam 2 (28 decks)

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