11.4 Lab + Lecture Notes

Question 1

What are single-celled glands

Answer 1

• simplest glands

- Ex. goblet cells of the intestine

Question 2

Compound acinar/tubuloacinar shaped glands are…

Answer 2

• always exocrine because implied apical lumen

- usually secrete via merocrine secretion

Question 3

Salivary glands

Answer 3

• paired glands (undergo involution with aging)
• 3 major salivary glands ( Parotid, submandibular, sublingual)
• most easily distinguished by nature of secretion - all by merocrine process
• primary branches = excretory duct - sits outside of the gland
• secondary branches = striated duct
• tertiary branch = intercalated duct

Question 4

Describe the secondary branch of the salivary gland

Answer 4

= striated duct

• simple columnar epithelium
• prominent basal striations
• FXN = ionic contant adjustment of fluid

Question 5

Describe the tertiary branch of salivary gland

Answer 5

= intercalated duct

• located between striated and secretory acini
• low cuboidal eithelium

Question 6

Describe the mixed seromucous acinus of the secretory glands and what is special about its appearance post preparation

Answer 6

• unique morphology due to artifact of standard preparations
  = serous demilune (not seen in freeze-fracture prep.) = swelling of mucus cells causing serous cells to bulge out towards BM

Question 7

What are zymogen granules

Answer 7

• stored proenzymes
• stain deeply eosinophilic
• use presence to help recognize the pancreas

Question 8

Describe the successive morphologies in pancreatic branching morphogenesis

Answer 8

1) Pancreatic duct (excretory)
2) Interlobular ducts
3) Intralobular ducts
4) Intercalated duct (w/ centroacinar cells) - clear cytoplasm + low cuboidal shape
5) Secretory acini

Question 9

Describe the centroacinar cells

Answer 9

• Unique ductal cell within the secretory acini of the pancreas
• represent the terminal extensions of the intercalated ducts
• morphology is like that of the duct = clear cytoplasm + low cuboidal cell shape

Question 10

How does the mesonephric kidney tissue develop

Answer 10

= branching morphogenesis

Question 11

How does the metanephric kidney tissue develop

Answer 11

• is induced by developing branches of the mesonephric tissue

Question 12

Overview of branching morphogenesis

Answer 12

= alternating repeating patterns of growth + differentiation

1) induction of epithelial growth through interaction with other tissues
2) structural elaboration through successive pages of growth + branching
3) morphological differentiation of growing structures through altered gene expression

Question 13

3 choices of glands

Answer 13

1) acinar = duct comes to point (won’t see lumen)
2) alveolar = spherical shpaed (ex. apocrine sweat gland)
3) tubular (like a test tube - eccrine sweat galnds)

Question 14

Describe the branching morphogenesis of the lung

Answer 14

• gut tube endoderm –> trachea –> segmental bronchi –> bronchioles –> club cells of bronchioles –> alveoli
• steps:
  1) trachea buds from endoderm (esophagus)
  2) bronchi + bronchioles from branching
  3) alveoli form through alteration of cells at tops of bronchioles

Question 15

Describe the 5 stages of lunch development

Answer 15

1) Embryonic
- 0-8wks
- lung bud ot tertiary bronchi
- 1 proliferation (finite number of branches maybe only 3 generations + fetal mesenchyme but can see visceral pleura and lung body plan)
2) Pseudoglandular
- 6-16wks
- bronchial branching to 21 generations
- branching + proliferation
3) Canalicular
- 16-26 wks
- alveolar sacs begin
= morphogenesis
- most CT has been filled by bronchi or branches of pulmonary circulation
- individual cells start looking like squamous cells of alveoli
4) Saccular
- 26wks - birth
- alveolar sacs mature
-start seeing proper alveoli
- still have significant CT
5) Alveolar stage
- 32wks-8years
- alveolar sacs multiply (proliferation)
- most CT gone except largest bronchi - similar to adult lung

Question 16

Describe the branching morphogenesis of salivary glands steps

Answer 16

1) bud forms from oral epithelium
2) elaboration creates branched ducts
3) specialized ductal cells accrue within lobes
4) secretory acini differentiate from tips of growing ducts

Question 17

Describe the branching morphogenesis organization of the salivary glands

Answer 17

1) excretory ducts
- how saliva gets to mouth
-“trunk of tree”
2) interlobular ducts
- between lobules within surrounding CT
3) intralobular ducts
-within lobules
4) striated ducts
- prominent basal striations
- see invaginations of BM into membrane (ion pumps) allow adjustment of [ionic]
- in LM see v. thin lines of radially stretched mitochondria
5) Intercalacted ducts
- smaller in morphology
6) acinar cells
= secretory cells

Question 18

Describe the branching morphogenesis organization of the pancreas

Answer 18

1) excretory ducts
- wirsung = major common duct
- santorini = small accessory duct
2) interlobular ducts
3) intralobular ducts
4) Intercalacted ducts
- bicarbonate adjustment
5) centroacinar cells
- bicarbonate secretion
- duct morphology in lumen of gland = cap of ductal portion of branch that sticks into lumen
= stem cells for secretory portion of the gland
6) acinar cells
= secretory cells - zymogen secretion

Question 19

Describe the branching morphogenesis steps of the pancreas

Answer 19

I) doral + ventral buds from from gut endoderm (duodenum) then fuse
II) first “Trunk” creates ducts (santorini + wirsung (forms common bile duct with sphincter of oddi)
III) successive differentiation gets the intercalated ducts –> centroacinar cells –> pancreatic acini

Question 20

Describe the endocrine pancreas embryology

Answer 20

• islets are derived from endoderm epithelium
• specifically in regions far from mesodermal tissue
• Zollinger-ellison syndrome = islet cell tumor of “G-cells” (gastrin producing)

Question 21

Describe the branching morphogenesis of the mammary glands steps

Answer 21

1) modified sweat glands, initial growth stimulated by underlying fat pods
2)growth + branching of ducts specifies lobes + lobules of breast
3) ductal tip cells (“stem cells” for secretory acini)
= precursors to mamary gland acini
- important in some types of breast cancer
4) acinar elaboration occurs with pregnancy (and ductal elaboration)

Question 22

Describe the branching morphogenesis organization of the mammary gland

Answer 22

A) lactiferous duct 
- trunk of tree
- majro exocrine glands
B) interlobular ducts
- see dense CT
forming breast stroma
C) intralobular ducts
- see loose CT
- immediately around gland
D) terminal ductules
E) acinar cells (milk secretion)
-milk only produced after pregnancy so acinar cells/terminal branching occurs in adulthood not embryology

Question 23

Describe the branching morphogenesis organization of the kidney

Answer 23

A) ureters
B) major + minor calyx
C) collecting duct
D) collecting tubule
E) nephron
- develops from unction by collecting tubule in surrounding mesenchymal tissue (metanephric tissue)

Question 24

Describe the branching morphogenesis steps of the kidney

Answer 24

1) branches of mesonephric tubule (future ureter) create lobes of kidney
2) successive branching creates collecting ducts –> form the center of renal lobules
3) instead of acini the tips of each ductule induce surrounding mesenchyme to form second tubular strcuture

Question 25

Describe the 5 specialization of branching morphogenesis highlighted in this class

Answer 25

1) Respiratory system
- conducting + respiratory airways
- alveoli (end branches_ inhibited from developing until end of embryogenesis
2) salivary glands
- parotid (pure serous)
- submandibular (seromucous, more serous)
- sublingual (seromucous, more mucous)
3) pancreas
- islets of langehans - separates from epithelium into CT
4) mammary glands
- adult morphogenesis
5) kidney
- collaboration of mesonephric + metanephric tissues
- collaboration fo different tissues forming discrete tubules