Digestive System Flashcards
What is the alimentary tract?
Tube extending from mouth to anus
Describe structure of alimentary tract
Muscular tube lined internally with epithelium
What is the function of alimentary tract
Ingestion, processing, digestion, absorption + excretion
What is the sequence of the digestive system?
Mouth —> pharynx —> oesophagus —> stomach —> small intestine —> large intestine —> anus
What is the pathway that food takes?
Oral cavity –> pharynx –> epiglottis –> oesophagus –> stomach –> duodenum –> jejunum –> ileum –> caecum –> ascending colon –> transverse colon –> descending colon –> sigmoid colon –> rectum –> anus
What is mucosa?
Type of epithelium
Moistened by glandular secretion
Describe structure of lamina propria
Mucosa
Loose connective tissue
Small blood vessels, lymphatics + nerve fibres
Immune cells
Describe structure of muscularis mucosa
Thin muscle layer
What is the submucosa?
2nd layer of loose connective tissue
Between mucosa + main muscle layers
Describe structure of submucosa
Blood vessels, lymphatic vessels
Neural tissue - submucosa plexus
What does the submucosa plexus do?
Regulates contractions + glandular secretions
What is the muscularis externa?
Smooth muscle typically divided into 2 layers
What are the 2 layers of the muscularis externa?
Inner = circular layer Outer = longitudinal layer
Why is it significant the muscularis externa have different layers?
Orientate in different directions
= contractions propel materials along tract
What is located between muscle layers in muscularis externa?
2nd nerve plexus
= myenteric plexus
What is the adventitia/serosa?
Covers muscularis externa
Describe alimentary canal position
Suspended in peritoneal cavity, covered in serosa
What are retroperitoneal organs covered in?
Adventitia NOT serosa
What is the oral cavity lined with?
Stratified squamous epithelium
What is function of oral cavity?
Ingestion + fragmentation of food
What is found in the oral cavity?
Salivary glands
Where are the salivary glands within the oral cavity?
Submucosa
What are the three salivary glands?
Sublingual
Submandibular
Parotid
What is the sublingual salivary gland?
Beneath tongue, many ducts
What is the submandibular salivary gland?
Floor of mouth, inner surface of mandible, ducts behind teeth
What is the parotid salivary gland?
Largest, empties at the molar
What is oral drug administration?
Given by mouth + swallowed
Easiest + safest BUT slow absorption
What is sublingual drug adminstration?
Placed under tongue - dissolves in saliva
Rapid absorption, high circulating levels
What is sublingual drug administration not used for?
Bad-tasting or irritating medications
What is buccal drug administration?
Placed in mouth next to cheek
Rapid absorption, high circulating levels
What is disadvantage of buccal drug administration?
Swallow pill
Describe mucosa in oesophagus
Above diaphragm = stratified squamous epithelium
Below = columnar epithelium
What is the mucosa in oesophagus?
Define lamina propria + muscularis
Describe muscularis externa in oesophagus
Striated muscle in upper 1/3
Smooth lower 1/3
What does muscle do in oesophagus?
Contract rhythmically towards stomach
What does the lower oesophagus sphincter prevent?
Reflux, emesis + regurgitation
What is involved in the lower digestive tract?
Stomach
Small intestine
Large intestine
How is the efficiency of absorption improved?
By increasing SA between epithelium + lumen
How is the SA increased?
Intrusions/folding
Inversions
Formation complex glands
What is the function of the stomach?
Reservoir + digestion
What does the stomach do?
Mixes food with gastric juices to form semifluid mass called chyme
How does stomach initiate protein breakdown + absorption of vitamin B12?
Release of intrinsic factor
What are the 4 anatomical regions of the stomach?
Cardia (closest to heart)
Fundus (upper area)
Body (middle portion)
Pylorus (narrow bottom)
Describe structure of gastric mucosa?
Columnar epithelium
Mucosa folded
Shallow depression on surface
Entire mucosa has simple tubular gastric glands
What do the cardiac gland do?
Mucus producing gland
Provide alkaline layer
What are the 4 cell types of corpus-fundic gland?
Chief cells
Parietal cells
Mucous neck cells
Endocrine cells
What do chief cells produce?
Pepsinogen
Gastric lipase
Chymosin
What do parietal cells produce?
Gastric acid
Intrinsic factor
What do endocrine cells do?
Stimulate secretion of other cell types
What do pyloric glands contain?
Endocrine cells, NO chief cells