Digestion System Flashcards
(54 cards)
What is digestion?
Breakdown of food to a useful form that can be absorbed and used by cells
Why do the cells use the absorbed ‘food’
Creation of energy
‘cellular respiration’ – ‘catabolism’
Production of ATP
pair / building
Production of ‘building blocks’ ‘anabolism’
What is mechanical digestion?
Physical breakdown
mastication / churning
What is chemical digestion?
Chemical breakdown (catabolic) acids / surfactants / ENZYMES
What does mechanical and chemical digestion do?
Liberating ‘useful’ components
amino acids, fatty acids, glucose, nucleotides
What are the major organs of the digestive system? (7) And accessory organs? (3)
The major parts of the digestive system: Salivary glands. Pharynx. Esophagus. Stomach. Small Intestine. Large Intestine. Rectum. Accessory digestive organs: liver, gallbladder, pancreas.
What are the digestive system processes? (5)
Ingestion Propulsion Digestion - Mechanical breakdown - Chemical breakdown Absorption Defecation
Recipe for saliva?
Water (~99%)
Amylase Lingual lipase Antibodies Lysozyme Defensins ‘Friendly bacteria
What are the four layers of the GI tract wall?
Serosa
Muscularis
Submucosa
Mucosa
Gastrointestinal tract layers
- serosa (adventitia)
- muscularis which includes longitudinal muscle and circular muscle.
- submucosa
- mucosa
Chyme in lumen
Function of the mucosa?
- Mucous membrane (protects, secretes, absorbs)
- Lamina propria (blood vessels, lymphoid tissue)
- Muscularis mucosa (provides infoldings)
Function of muscular layer
2 layers of smooth muscle
(circular & longitudinal)
Provides peristalsis and mixing
Onward movement regulated by sphincters
Function of the submucosa?
Loose connective tissue Blood vessels Nerves Lymph vessels Lymphoid tissue
Function of the adventitia/serosa?
Outermost layer
In abdomen = peritoneum
Barrier to spread of infection
Anchors GI tract
What is the mesentery?
The mesentery is a fold of membrane that attaches the intestine to the abdominal wall and holds it in place.
What are Mesenteric lymph nodes (MLNs)?
Mesenteric lymph nodes (MLNs) are an important site of T-cell activation for both the SI and colon. DCs continually migrate from intestinal tissues to the MLNs where they present antigen and control the development, migration, and functional differentiation of cells of the adaptive immune system
What is peristalsis?
Peristalsis, involuntary movements of the longitudinal and circular muscles, primarily in the digestive tract
What is the enteric nervous system?
The enteric nervous system (ENS) is a large division of the peripheral nervous system (PNS) that can control gastrointestinal behaviour independently of central nervous system (CNS) input.
Five facts about the oesophagus
Conveys food oropharynx → stomach
Mucosa subject to considerable friction
Thick protective stratified squamous epithelium
Passage of food facilitated by:
Flattening of mucosal folds
Mucous glands (G)
Loose and elastic submucosa (SM)
Muscularis externa
Upper ⅓: skeletal muscle (initiation of swallowing voluntary)
Lower ⅔ : smooth muscle only (peristalsis)
Glands of the stomach fundus and body
- Surface mucous cells
- Mucous neck cells simple columnar
Secrete acidic mucus - Parietal cells secrete HCl & intrinsic factor
- Chief cells secrete pepsinogen, lipases
- G –cells Secrete gastrin
Three parts of the small intestine
Duodenum
Jejunum
Ileum
Function of the small intestine
Glands secrete intestinal juice
Completes chemical digestion
Absorption of nutrients
What are the mucosal folds made up off and what is the function?
villi and microvilli increase surface area for digestion and absorption
Name the cells in the small intestine.
- Absorptive cells
- Goblet cells
(Mucus) - Intestinal crypt
(crypt of Lieberkuhn) - Paneth cells
Defensins
Lysozyme - Secretory cells
Intestinal juice - Entero-endocrine cells
Secretin
Cholecystokinin