week 9 sem 2 Flashcards
The functions of the digestion system include
ingestion, secretion, Mechanical processing, digestion, absorption, Defecation
The four major layers of the digestive tract are the;
mucosa, Submucosa, Muscularis, serosa
mucosa
Inner lining of the digestive tract
Consists of an epithelium, moistened by glandular secretions
Epithelium varies with location, function and the stresses placed on it
The locations that encounter severe mechanical stresses, e.g., the oral cavity, pharynx and oesophagus, are lined with stratified squamous epithelium
The locations where absorption occurs, e.g. stomach, small intestine and large intestine, are lined with simple columnar epithelium with goblet cells
submucosa
Dense, irregular connective tissue beneath the mucosa
Has numerous blood vessels and lymphatic vessels and a network of sensory neurons
In some locations, it contains glands that secrete buffers and enzymes into the lumen of the digestive tract
Binds the mucosa to the muscularis externa
Muscularis
Dominated by smooth muscle cells
The inner circular layer is essential for agitation and in the formation of valves
The outer longitudinal layers of muscle is essential for mechanical processing and in moving materials along the digestive tract
serosa
Covers the muscularis externa along most portions of the digestive tract
oral cavity functions
- ingestion
- sensory analysis of food before swallowing
- lubrication by mixing with mucus and saliva
- mechanical digestion through the actions of the teeth, tongue and palatal surfaces
- initiation of carbohydrate digestion by salivary amylase
- initiation of lipid digestion by lingual lipase
salivary glands
Thought, smell, taste, chewing action, and presence of food in the mouth induces saliva production
pharynx
The pharynx is a passageway for solid food, liquid and air. Swallowing is the process that allows for a substance to pass from the mouth, to the pharynx, and into the oesophagus. Once food moves into the pharynx it is now called a bolus.
oesophagus
The oesophagus is a hollow muscular tube, posterior to the trachea, that conveys solid food and liquids to the stomach. The oesophagus wall contains large folds that extend along the length and allow for expansion during the passage of a large bolus. Muscle tone in the walls keeps the lumen closed, except when you swallow
liver fuctions
- metabolic homeostatis
- Haematological regulation
- Bile production
gall bladder
gall bladder stores and concentrates bile prior to its excretion into the small intestine
stomach
The stomach is a distensible organ that connects the oesophagus to the duodenum and temporarily stores ingested food.
pancreas
The pancreas is both an endocrine and exocrine organ.
Endocrine – because it secretes the hormones, insulin and glucagon into the bloodstream.
Exocrine – because it secretes pancreatic juice into the duodenum.
Large intestine
- Caecum – an expandable pouch that receives the chyme from the ileum, starting the process of compaction.
- Colon – the largest portion of the large intestines.
- Rectum – last part of the digestive tract. It is an expandable organ for the temporary storage of feces.
- compacts and stores feacal material prior to defecation
- produces mucous for lubrication of faecal material
- reabsorbs water and other useful substances such as electrolytes, vitamins and bile salts
Mechanical digestion (processing)
- Mouth
- Mastication
- Oesophagus
- Peristalsis
- Stomach
- Mixing, churning
- Peristalsis
- Small intestine
- Segmentation
- Peristalsis
