1.1 Introduction to the GIT Flashcards
What is prehension?
Act of getting food into the mouth. Domestic animals do this by using their lips, teeth, tongue and by head and jaw movements
What is mastication?
Involves the mechanical breakdown of food and allows mixing with saliva
What is deglutition (swollowing)?
Occurs in several phases
- initial phase is voluntary
- remaining phases are under involuntary control
What are the functions of the salivary glands and saliva?
- moisturise and lubricate food
- amylase: breakdown carbohydrates
- aids mastication, bolus formation, enzymatic formation and swallowing
What are the basic secretory units of salivary glands?
acini
What are the three major pairs of salivary glands and what do they produce?
- parotid glands - produce a serous, watery secretion
- submaxillary (mandibular) glands - produce a mixed serous and mucous secretion
- sublingual glands - secrete a saliva that is predominantly mucous in character
Describe the two basic types of acinar epithelial cells
- serous cells: secrete a watery mucous essentially devoid of mucus
- mucous cells: produce a very mucous rich secretion
Describe the function of the oesophagus
Transportation of food
Describe the anatomy of the oesophagus
- Longitudinal musculomembranous tube
- Length divided in: cervical, thoracic and abdominal parts
- initiates the alimentary canal
- extends from pharynx to stomach
- average diameter: 1-2 inches
Describe the histology of the mucosa of the oesophagus
Nonkeratinised stratifies squamous epithelium that covers all oesophageal lumen
Describe the histology of the submucosa of the oesophagus
Elastic and fibrous collagen that form a dense, irregular connective tissue
- consists of lymphatic and blood vessels
Describe the histology of the tunica muscularis of the oesophagus
Both longitudinal and circular muscles form tube like oesophagus
- longitudinal muscle fibres are located superficially
- circular muscles are located deeply
Describe the histology of the serosa/adventitia of the oesophagus
Surrounds most of the oesophagus and consists of loose connective tissue
Describe the general anatomy of the stomach
- saclike expansion
- between oesophagus and small intestine
What is the function of the stomach?
Temporary food container before it is passed into the intestine
Enzymatic breakdown of food
What is the function of rugae?
Folds that increase the surface area so digestion can be optimised because the enzymes being secreted by the glands of the stomach have more space to interact with food
What are sphincters in the stomach?
Ring shaped muscular structures that can contract + relax, control the passage of food
- Cardiac/lower oesophageal sphincter
- pyloric sphincter
Describe the histology of the mucosa of the stomach
Inner layer interacts with food
- full of gastric glands and pits and a layer of smooth muscle - muscularis mucosa
Describe the histology of the muscularis externa of the stomach
Three layers of muscle: an inner oblique layer, a middle circular and an external longitudinal layer
What are psudoruminants?
Have a 3 chamber stomach
- camelids and hippos
Describe the anatomy of the small intestine
Initiates after the stomach, ends in the ileum right before large intestine
What are the 3 parts of the small intestine?
- Duodenum
- lining secretes mucous and fluids
- bile duct
- pancreatic duct - Jejunum (largest part of the small intestine) + 3. Ileum
- secretes fluids
- accomplishment of chemical digestion
- nutrient absorption
Describe the anatomy of the liver
Located cranially to the stomach
- lobed
- functional unit = hepatocytes
What functions do the hepatocytes provide?
- synthesis of bile
- storage (energy)
- biotransformation
- synthesis of blood compartments
Describe histologically the liver
Sheets of connective tissue divide the liver into thousands of small units called lobules
- lobules; roughly hexagonal in shape, with portal triads at the vertices and a central vein in the middle
Describe anatomically the pancreas
In all vertebrate species
Right side of the abdomen, adjacent to proximal duodenum - pancreatic duct
- blood supply = splenic artery
- divided into lobules by connective tissue (septae)
What is the compound gland?
Clusters of exocrine cells inside the lumen of small intestine
Endocrine cells - pancreatic islets of langerhans which are secreted in the bloodstream
Describe anatomically the large intestine
Initiates after the ileum, ends in anal canal
What are the 5 parts of the large intestine?
- Caecum - digestion of cellulose by microflora in many animals especially herbivores (hindgut fermenters)
- Ascending colon
- Transverse colon
- Descending colon - absorb water and ions - compaction of undigested material and microflora
- Rectum - expel faeces
Describe the anatomy of the caecum
Between ascending colon and ileum
- starts after the ileocaecal junction
Compare the caecum of canine, equine, porcine and ruminant species
Canine: on right side of the abdomen, no direct connection to the ileum, short and held by the ileocaecal fold, little microbial fermentation takes place
Ruminant: right side of the abdomen in the supraomental recess, little microbial fermentation takes place
Equine: significant amount of fermentation, formed by haustra & tenia, very large, point cranially
Porcine: left side of the abdomen with apex pointing caudoventrally
Describe the anatomy of the colon
Tubular structure
Muscular layers
What are the histological layers in the colon?
Tunica muscularis, serosa, submucosa, mucosa
What is coprophagy?
In rabbits, eat their own faeces and digest it for a second time to ensure all of the nutrients have been absorbed
