HUMB1001 Lecture Notes - Lecture 9: Stratified Squamous Epithelium, Simple Squamous Epithelium, Mesentery
Digestive System – From Plate to Bowl
• Mouth (oral cavity)
• Pharynx (throat)
• Oesophagus (gullet)
• Stomach
• Small intestine
o Duodenum, jejunum, ileum
• Large intestine
o caecum, appendix
o colon – ascending, transverse,
descending & sigmoid
o rectum & anal canal
o anus
Major Function
1. Ingestion
2. Mastication (chewing)
3. Propulsion
- deglutition (swallowing)
- peristalsis
- mass movements (large intestine)
4. Mixing
- segmental contraction
5. Secretion
- mucus, H2O, bile, enzymes, HCl
6. Digestion
- mechanical
- chemical
7. Absorption
- movement from lumen of tract into circulation – (blood/lymph)
8. Elimination (egestion)
- defaecation
Histology – Layers of the Gastrointestinal Tract
1. Mucosal layer
2. Submucosal layer
3. Muscularis externa layer
4. Serosa layer
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Layer 1: Mucosa (3 sublayers)
a) Epithelium
- Non-keratinised stratified squamous
o Mouth, oesophagus, anus
- Simple columnar (secretory)
(remainder of the tract)
o Secretes enzymes, acid & absorbs nutrients
o Specialised cells (goblet) secrete mucus
o Contains entero-endocrine cells
b) Lamina propria
- Thin layer of loose C.T
- Contains blood & lymphatic vessels & lymphoid tissue
c) Muscularis mucosae
- Thin layer of smooth muscle
- Tithig oeets
- Tone → folds of small intestine
Layer 2: Submucosa
❖ Loose connective tissue
o BVs
o Lymphatics
o Lymphoid follicles
o Glands
o Nerves – Meissers pleus
(ANS, enteric):
▪ Vasoconstriction
▪ Local movement by
smooth muscle of muscularis mucosae
▪ Promotes glandular secretions
Layer 3: Muscularis Externa
❖ 1. Inner circular
2. Outer longitudinal fibres
*innermost oblique fibres in the stomach
❖ Skeletal muscle = voluntary control
o Mouth, pharynx, upper oesophagus & anus
o Control over swallowing & defaecation
❖ Smooth muscle = involuntary control
o Propels food along by peristalsis
o Mixes food by segmentation
❖ Auerahs pleus eteri
o Both PNS & SND & enteric innervation of circular & longitudinal smooth
muscle layers
o Control over gut movements
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Peristalsis & Segmentation
Layer 4: Serosa (visceral peritoneum)
❖ Part of abdominal serous membrane
o Visceral: covers organs
o Parietal: covers interior surface of body wall
❖ Consists of loose C.T covered with (simple squamous epithelium)
❖ Covers all organs & lines walls of abdominal cavity
❖ Secretes serous (serum-like) fluid
❖ Forms folds that suspend organs
Retroperitoneal:
Certain organs covered by peritoneum on only one surface & are considered to be behind
the peritoneum
❖ kidneys, pancreas, duodenum
Peritoneum
❖ Mesenteries
o Two layers of peritoneum with thin layer of
loose C.T. between
o Routes by which vessels and nerves pass
from body wall to organs
o Greater omentum: connects greater
curvature of stomach to transverse colon
o Lesser omentum: connects lesser curvature
of stomach & proximal part of duodenum
to liver and diaphragm
o Transverse mesocolon, sigmoid mesocolon,
mesoappendix
❖ Ligaments
o Coronary: between liver and diaphragm
o Falciform: between liver and anterior abdominal wall
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Document Summary
Digestive system (cid:862)from plate to bowl(cid:863: mouth (oral cavity, pharynx (throat, oesophagus (gullet, stomach, small intestine, duodenum, jejunum, ileum. Large intestine: caecum, appendix, colon ascending, transverse, descending & sigmoid rectum & anal canal, anus. Mass movements (large intestine: mixing segmental contraction, secretion. Mucus, h2o, bile, enzymes, hcl: digestion. Movement from lumen of tract into circulation (blood/lymph: elimination (egestion) Histology layers of the gastrointestinal tract: mucosal layer, submucosal layer, muscularis externa layer, serosa layer. Non-keratinised stratified squamous: mouth, oesophagus, anus. Simple columnar (secretory) (remainder of the tract: secretes enzymes, acid & absorbs nutrients, specialised cells (goblet) secrete mucus, contains entero-endocrine cells, lamina propria. Contains blood & lymphatic vessels & lymphoid tissue: muscularis mucosae. Loose connective tissue: bvs, lymphatics, lymphoid follicles, glands, nerves meiss(cid:374)er(cid:859)s ple(cid:454)us (ans, enteric), vasoconstriction. Local movement by smooth muscle of muscularis mucosae: promotes glandular secretions. Skeletal muscle = voluntary control: mouth, pharynx, upper oesophagus & anus, control over swallowing & defaecation.
