Chapter 15 - Digestive Tract Flashcards
1
Q
Functions of DT
A
- ingestion
- mechanical processing and propulsion
- chemical digestion
- absorption
- elimination
- surveillance and defense against toxic molecules and pathogens
2
Q
Serosa
A
- outermost layer
- visceral peritoneum
3
Q
Muscularis (muscularis externa)
A
- second outermost layer
- smooth muscle
- outer, longitudinal layer is parallel to length of DT
- inner, circular layer
- Auerbachs’ plexus
4
Q
Submucosa (muscularis mucosa)
A
- second innermost layer
- may contain nerve plexuses (Meissner’s), glands, lymphoid folllicles
5
Q
Mucosa
A
- Innermost layer
- lamina propria - loose CT that underlies the epithelium of the mucosa
- glands, villi
- simple columnar epithelium (lines stomach to the colon)
6
Q
Oral cavity
A
- lined with stratified squamous epithelium (mainly nonkeratinzed)
- digestion begins here - both mechanical and chemical (amylase)
7
Q
Esophagus
A
- stratified squamous epithelium
- esophageal glands in submucosa
- upper portion has skeletal muscle in musclaris externa
- lower portion has smooth muscle, forms gastroesophageal sphincter
8
Q
Stomach
A
- transforms material from oral cavity into chyme
- chemical digestion begins in earnest here
- gastric juice contains HCl, pepsinogen and intrinsic factor
- hormone gastrin stimulates motility in the stomach and the release of pepsinogen
9
Q
Muscularis externa of stomach
A
- 3 layers of smooth muscle - aids in churning and mixing of food with pepsin and HCl
- outer - longitudinal
- middle - circular
- inner - oblique
10
Q
Gastric juice of stomach
A
- HCl
- pepsinogen - made by gastric cells and cleaved into pepsin in low pH - pepsin begins protein cleavage of food
- intrinsic factor binds vitamin B12 which is absorbed in the ileum
11
Q
Small intestine
A
- duodenum, jejunum, ileum
- majority of chemical digestion and nutrient absorption occurs here - secretion from liver and pancreas released into duodenum
- mucosa has large surface area for absorption
12
Q
Structure of SI
A
- plicae circulares - large folds of mucosa and submucosa - mainly in jeju
- villi - upward extension of epitheium and lamina proporia
- covered w/ columnar epithelium (absorption, have microvilli on surface)
- glands (crypts of lieberkuhn) - mucus secretion
- lymphocytes
- lymphoid nodules (Peyer’s patches) in lamina propria and submucosa
13
Q
What do the microvilli in the SI do?
A
- goblet cells secrete mucus
- Paneth’s cells make lysozyme that breaks down peptidoglycan in bacterial cell walls
14
Q
What are microvilli on enterocytes in the SI called?
A
brush border
15
Q
Absorption in SI
A
- columnar epithelial cells take up sugars, peptides, amino acids and lipids
- lipids converted to chylomicrons and released into lacteals in villi and go to liver first through lymphatic capillaries
- other nutrients released into capillaries in villi
