+ Motivational Corner:

“Step through new doors. The majority of the time there's something fantastic on the other side.”

Objectives: 1- By the end of this lecture, the student should be able to discuss Integrated the microscopic structure in & . correlation with the function of the following organs: 1. Esophagus. 2. Stomach. Extra notes: Gray Important notes: Red + Alimentary Canal

Is the tubular portion of digestive system.

Subdivided into

Large intestine (, colon, Esophagus. Stomach. (, , , and ). and ).

Mucosa. General or Serosa Architecture . of L/M Structure of Alimentary Muscularis externa. Canal OR serosa. + Esophagus

■ Four concentric layers:

Mucosa Submucosa Muscularis Serosa or externa Adventitia

Epithelial Lining: • Loose areolar C.T. • Two muscle layers: • Adventitia: is loose Non-Keratinized containing blood 1-Inner circular layer. areolar C.T. not Stratified Squamous vessels, nerves, 2-Outer longitudinal layer. covered by Epithelium. submucosal mesothelium. esophageal glands • Upper 1/3: both layers In the thoracic part of are skeletal M. : (secretion of ) the esophagus. Loose areolar C.T. with • Middle 1/3: inner layer is mucosal esophageal • Meissner’s plexus glands (secretion of • Outer layer is skeletal • Serosa: is loose of nerve fibers and mucus) in the upper and M. areolar C.T. covered nerve cells. • Lower 1/3: both layers lower ends. by mesothelium are smooth M. (simple squamous • Auerbach’s : (myenteric) plexus in epithelium) Few layers of smooth between the 2 layers in the abdominal part muscle fibers. of the esophagus.

Serosa

Submucosal esophageal gland Auerbach’s plexua + Stomach

It has 4 regions: Mucosa has folds, • Cardia known as rugae • Fundus • Body that disappear in • the distended stomach.

Fundus (and Body) of Stomach

• Is invaded by fundic glands. The surface epithelium of the mucosa is simple columnar mucus-secreting cells. Mucosa Surface Columnar Epithelium: Simple columnar epithelium: secretes mucus. • Connective tissue containing blood vessels, nerves, and Meissner’s plexus. Sub Mucosa of Lamina propria: C.T. invaded • NO glands. by numerous fundic glands mucosa: Fundus of with lymphoid elements. Stomach Three smooth muscle layers: (Inner oblique - Middle circular - Outer longitudinal.) Muscularis mucosae: 2 layers of smooth muscle fibers. Muscularis Auerbach’s (myenteric) plexus. Externa:

• C.T. covered by mesothelium. (Not adventitia) Serosa There are NO goblet cells in the stomach. + Fundic Glands

Short pits: one fourth of mucosa. Fundic glands Simple branched tubular glands. have: Are rich in parietal & chief cells.

1- Lumen.

2- Surface columnar epithelium.

Mucosa of 3- Pits of fundic glands. Fundus of 4- Fundic glands. Stomach 5- Lamina propria.

6- Muscularis mucosae.

Fundic Glands Composed of 5 cell types:

Parietal (oxyntic) cells: Shape: pyramidal or polygonal. Nucleus: central, round. Cytoplasm: Deeply acidophilic, rich in SER and mitochondria (40% of the cell volume). C-shaped intracellular canaliculus.

Secrete HCl and gastric intrinsic factor that helps absorption of vitamin B12.

Peptic (chief) cells The predominant cell type. Columnar cells. Nucleus: basal, round. Cytoplasm: basohilic with apical secretory granules. Secrete pepsinogen.

Mucous neck cells Secrete mucus.

Enteroendocrine (EE) (DNES) Enterochromaffin (EC) cells: secrete hormones (e.g. serotonin, endorphin). cells:

Stem cells Regenerative cells. + Pylorus of stomach • Is invaded by Pyloric glands. The surface epithelium is simple columnar mucus-secreting cells. Mucosa

• Connective tissue containing blood vessels, nerves, and Meissner’s plexus. Sub • NO glands. mucosa:

Two smooth muscle layers: (Inner circular - Outer longitudinal.) Muscularis Auerbach’s plexus. Externa:

• C.T. covered by mesothelium. (NOT adventitia) Serosa

1- Lumen.

2- Surface epithelium.

3- Pits of pyloric glands.

4- Lamina propria.

5- Muscularis mucosae.

6- Submucosa

7- Muscularis externa

Their pits are deep, about half the length of Pyloric mucosa. glands have: They are branched and convoluted, many cross sections.

Cells of pyloric gland:

Mucus neck cells EE cells Stem cells Parietal cells No peptic cells (Mucus secreting cells)

1- The predominant cells 1- EC cells - Few Because parietal 2- Secrete mucus. 2- G cells cells which secrete 3- D cells pepsinogen are few. 4- A cells Summary + Esophagus Stomach Layers Fundus Pylorus

Non- Surface epithelium: D 5

Keratinized Simple columnar mucus- B 4

Mucosa Stratified secretingcells. B 3

Squamous Fundicglands. Pyloricglands. C 2

Epithelium. Short pits (1\4of Deep pits(1\2 C 1 mucosa). ofmucosa). Glands. NO glands. Submucosa Meissner’s plexus. Musculs 2 smooth musclelayer. 3layers. 2layers. externa Auerbach’splexus. Serosa Serosa in the OR abdominal part Serosa. adventita of the esophagus Or adventitia.

MCQs

Q1- Which one of the following contains Q4- Which one of the following cell type of glands in it’s submucosa ? funds glands help in absorption of Vitamin a) Fundus of stomach B12 ? b) Pylorus of stomach a) Peptic cells c) Esophagus b) Parietal cells c) Enteroendocrine cells

Q2- Which one of the following is the Q5- What type of muscle makes up the predominant cell in Fundic glands ? muscularis externa in the esophagus? a) Mucus neck cells a) Smooth b) Parietal cells b) Striated c) Peptic cells c) Cardiac d.) both a and b Q3- which one of the following is the e) a, b, and c. Thanks you for checking predominant cell in pyloric glands ? our work, Good luck. a) Parietal cells -Team histology. b) Mucus neck cells c) Enteroendocrine cells Done by: Areeb ALOgaiel Sadeem Alqahtani Hanan Alabdullah For any question or suggestion: Team leaders: [email protected] Areeb AlOgaiel Fawzan AlOtaibi