Digestive Sytem Flashcards
What are the main functions of the human digestive system?
Digestion and absorption
Conversion of food to nutrients
Hydrolysis of some compounds
Motility and mechanical breakdown of food
Secretion and excretion
Defence
Outline the development of the gastrointestinal tract?
The main structure develops from the mesoderm
Epithelial internal linking from the endoderm
Neurons of the GI tract from the neural crest (ectoderm)
List the components of the upper gut
Mouth
Oesophogus
Stomach
Duoderm
Jejunum
Ileum
List the components of the small intestine
Duoderm- Main secretory part of small intestine
Jejunum
Ileum- main site of absorption
List the components of the large intestine
Caecum- Fermentation site, principal site of microbial action
Colon
Rectum and anus- Storage and control
What are sphincters?
Functional boundaries between gut sections
They prevent back flow and deliver food to functional regions
What is the connection of the digestive system to the CNS?
Most functions are autonomic
Parasympathetic actions at the vagal nerve and sympathetic action from the pre vertebral ganglia, which act as antagonists
What is the connection of the digestive system to the rest of the body?
The blood Exeter the system form 3 main arteries:
Coeliac, Superior and Inferior mesenteric
Hepatic portal vin moves gut metabolites to the liver
Fat soluble material handled via lymphatic system
How is the digestive system organised at a tissue level?
Separated form the rest oft eh body by a single layer of epithelial cells
This include south circular and longitudinal layer of muscles that make up the muscular is externa
Serosa= outer lining of the internal organs
Mucosa= connective tissue that supports epithelial lining and structure
Outline the process of digestion
Mechanical digestion breaks down food structure
Chemical digestion produces absorbable components:
CHO’s into monosaccharides
Proteins into amino acids
Triglycerides into fatty acids and glycerol
Describe the mouth and its role in digestion
Mouth= a mechanical and biochemically digestive organ
Known as “food mill”= first phase of digestion that eases swallowing and aids gastric digestion
Amylase in saliva breaks down sugar
What is the importance of the tongue and teeth in digestion?
Teeth allow for texture analysis, contain nerves that relay to the CNS for texture interpretaiton
Papillae all over the tongue= tastebuds
Circumvallate= sequester saliva from the back of the out to lubricate food
Describe oesophageal peristalsis
Process of food being pushed into stomach and the start of digestion
Peristalsis= Autonomic rhythmical smooth muscle movement to massage ingested food away from the mouth
List and describe the gastric function of the stomach
Food storage- regulates flow of digesta into the small intestine
Mechanical digestion- liguefies food and releases it slowly into the small intestine
Protection- reduces risk of noxious entering small intestine due to acid barrier
Chemical digestion- contains pepsin f protein digestion
Secretes intrinsic factor- for vB12 absorption
Self-protection- mucus secretion
Control of gastrointestinal processes- release of hormones
How is the gastric gland organised?
Mucus cells- secrete an alakaline mucus that protects the epithelium against shear stress and acid
Parietal cells- secret HCL, important for maintenance of pH
Chief cells- secrete pepsinogen that breaks down dietary proteins, not active unless exposed to HCL
G cells- secrete gastrin (hormone)
