Micro HSB - Digestive System Development and Histology

Epithelial lining and glands

Germ layer present at 2 weeks - ENDODERM (2)

Lamina propria, muscularis mucosae, submucosa, muscular serosa and externa

Germ layer present at 2 weeks - MESODERM (5)

Enteric nervous system and posterior luminal digestive structures

Germ layer present at 2 weeks - ECTODERM (2)

3-4 weeks, yolk sac

The PRIMITIVE GUT develops at weeks _____ to _____, by incorporating _________ during the craniocaudal and lateral folding of the embryo.

Foregut

Esophagus, liver, gallbladder, stomach, bile duct, pancreas, and proximal duodenum is classified as

Midgut

Distal duodenum, jejunum, ileum, cecum, appendix, ascending colon, 2/3 of transverse colon is classified as

Hindgut

1/3 of transverse colon, descending colon, sigmoid colon, upper anal canal is classified as

Cloaca

Endoderm-lined cavity covered at its ventral boundary by surface ectoderm

A: pharynx

Identify the structure

A: dorsal aorta

B: esophagus

C: trachea

Identify the structure

A: stomach

B: liver

Identify the structure

A: dorsal mesentery

B: dorsal pancreatic bud

C: stomach

D: liver sinusoid

Identify the structure

A: dorsal pancreatic bud

B: duodenum

C: liver sinusoid

Identify the structure

A: dorsal pancreatic bud

B: ventral pancreatic bud

C: duodenum

Identify the structure

A: dorsal pancreatic bud

B: ventral pancreatic bud

C: duodenum

D: liver

Identify the structure

A: duodenum

B: cystic duct

C: gallbladder

D: liver

Identify the structure

A: mesocolon

B: colon

Identify the structure

A: physiologic herniation of intestinal loop

Identify the structure

A: physiologic herniation of intestinal loop; week 10-12

Identify the structure; it returns back to the abdominal cavity at weeks _____

A: physiologic herniation of intestinal loop; week 10-12

Identify the structure; it returns back to the abdominal cavity at weeks _____

A: cloaca

B: urorectal septum

C: urogenital canal/sinus

D: anal canal (anorectal canal)

Identify the structure

• mucosa

• submucosa

• tunica muscularis/muscularis propria

• tunica adventitia/tunica serosa

4 layers of the digestive tract

• lining epithelium

• lamina propria

• muscularis mucosa

3 layers of the mucosa of the digestive tract

Scanner View of ESOPHAGUS

A: mucosa

B: submucosa

C: tunica muscularis

D: tunica adventitia/serosa

Identify the structure

LPO - MUCOSA OF ESOPHAGUS

A: lining epithelium

B: lamina propria

C: muscularis mucosa

Identify the structure

Stratified squamous non-keratinized epithelium

Lining epithelium of the structure

Loose connective tissue with scattered lymphocytes; (+) superficial esophageal glands

Lamina propria of the structure

Morphology: branched coiled glands

Location: lower end of esophagus

MORPHOLOGY and location of lamina propria of structure

Single layer of smooth muscle

Muscularis mucosa of the structure

• Submucosa of esophagus

• Dense irregular connective tissue

• Meissner’s plexus

• Deep esophageal glands

Identify the structure, its arrangement, and contents found in it (2)

Meissner’s plexus and deep esophageal glands

Structures found in the submucosa of esophagus with mucus secretion function (2)

• tunica muscularis of esophagus

• inner circular, outer longitudinal

• myenteric/auerbach’s plexus

Identify the structure, its arrangement, and contents found in it (1)

For peristalsis and motor movement; tunica muscularis of esophagus

Function of Auerbach’s/myenteric plexus and its location

upper: skeletal muscle

middle: skeletal and smooth muscle

lower: smooth muscle

Tunica muscularis of the upper 1/3, middle 1/3, and lower 1/3

• tunica adventitia of the esophagus

• loose CT

• blood and lymph vessels

Identify the structure, its arrangement, and contents found in it (2)

Gastroesophageal junction or squamocolumnar junction

Identify the structure

SC: simple columnar (stomach)

SSNK: stratified squamous non-keratinized epithelium

A: mucosa

B: submucosa

C: tunica muscularis

D: tunica adventitia/serosa

Identify the structure

Scanner view of STOMACH

A: mucosa

B: submucosa

C: tunica muscularis

Identify the structure

A: smooth muscle (peripheral nuclei)

B: skeletal muscle (central nuclei)

Identify the structure 

Scanner view of STOMACH

A: mucosa

B: submucosa

C: tunica muscularis

Identify the structure

LPO view of STOMACH

E: submucosa

A: internal oblique

B: middle circular

C: outer longitudinal

D: tunica serosa/adventitia

Identify the structure

STOMACH

A: rugae

B: surface mucus and mucus neck cells

C: parietal or oxyntic cells

D: chief/principal/zymogenic cells

E: mucosal folds

F: submucosa

Identify the structure

STOMACH

A: mucosa

B: gastric pits

C: gastric glands

D: muscularis mucosa

E: submucosa

Identify the structure

LPO - STOMACH MUCOSA

A: LE (simple columnar epithelium without goblet cells)

B: Mucous neck (columnar) cells

Identify the structure, its arrangement, and cell found in it (1)

Gastric Mucosa of STOMACH

A: mucus cells

B: parietal/oxyntic cells

Identify the structure

Mucous neck (columnar) cells

Cell in the stomach that produces a thick coating of mucus, that protects the gastric mucosa from acid and enzyme secretion

LPO - LAMINA PROPRIA OF STOMACH

• gastric glands - synthesis and secretion of gastric juice

Identify the structure and content found in it (1)

LPO - Gastric glands in the lamina propria

• Parietal or Oxyntic Cells - secretes HCL and intrinsic factor; eosinophilic

Identify the structure

LPO - Gastric glands in the lamina propria

• chief/peptic/zymogenic cells - most numerous, basophilic, and secretes pepsinogen and gastric lipase

Identify the structure

E: submucosa of stomach

LE: dense connective tissue

Has: Meissner’s corpuscles, blood and lymphatic vessels

No: gastric glands

Identify the structure E, its lining epithelium, and content found in it (3)

Tunica muscularis of stomach

• inner oblique

• middle circular

• outer longitudinal

Identify the structure and muscle arrangement

Small Intestine

LE: simple columnar with goblet cells

LP: loose CT

MM: 2 thin layers of smooth muscle

Lining epithelium, lamina propria, and muscularis mucosa of the small intestine

SMALL INTESTINE

• dense ct with bv, ln, and meissner’s plexus

Describe the submucosa of the small intestine

A: intestinal gland

B: columnar cells/enterocytes

C: goblet cells

D: paneth cells

Identify the structures found in the small intestine

Paneth cells

Identify the structure

SMALL INTESTINE

Left: meissner’s plexus

Right: myenteric/auerbach’s plexus

Identify the structure

DUODENUM

• Brunner’s gland or duodenal glands

  • secrete alkaline fluid composed of mucin as protection for acidic chyme from stomach

Identify the structure

DUODENUM

A: mucosa

B: submucosa

C: tunica muscularis

D: tunica serosa/adventitia

E: intestinal glands

Arrow: Brunner’s gland

identify the structure

JEJUNUM

• prominent plicae circularis

  • increase surface area = increase absorption 

Identify the structure and its characteristic feature

JEJUNUM

A: mucosa

B: submucosa

C: tunica muscularis

D: tunica serosa

Identify the structure

ILEUM

• peyer’s patches

  • lymphoid nodular aggregates

Identify the structure and its characteristic feature

ILEUM

• peyer’s patches

  • lymphoid nodular aggregates

Identify the structure and its characteristic feature

ILEUM

A: villi

B: peyer’s patch

C: submucosa

Identify the structure

ILEUM

A: muscularis mucosa

B: lamina propria

C: lining epithelium

D: peyer’s patch

E: crypts or lieberkuhn (intestinal glands)

F: submucosa

Identify the structure

Appendix

A: mucosa

B: submucosa

C: muscularis mucosa

D: tunica adventitia

E: intestinal glands in lamina propria

Arrow: lymphatic nodules

Identify the structure

COLON

• goblet cells

• plenty of goblet cells in the intestinal gland

Identify the structure and its parenchyma

F: no more intestinal villi

T/F: The structure has intestinal villi

T

T/F: Crypts of Lieberkuhn are still present and usually longer and straighter than that of small intestine

COLON

• intestinal glands with plenty of goblet cells

Identify the structure

Recto-anal junction

A: rectum (simple columnar with goblet cells)

B: anus (stratified squamous non-cornified epithelium)

Identify the structure

rectum

Goblet cells are most numerous in this segment of the large intestine

rectoanal junction

• simple columnar rectum to stratified squamous non-cornified anus

identify the structure