Overview of the Alimentary Tract Flashcards
What is a carnivore?
- high energy content
- muscle, blood, adipose tissue
- easily digested
- short, simple digestive tract
What is a herbivore?
- energy from plant material in form of carbohydrates which cannot be broken down by enzymes produced by animal itself
- large microbe containing chambers in the digestive tract
What is an omnivore?
- plant and animal origin - large species variation
Alimentary system or gastrointestinal system consists of what?
- headgut
- foregut
- midgut (small intestine)
- mid/hindgut (large intestine)
What components and glandular organs are associated with the headgut?
- mouth
- pharynx
- oesophagus
- salivary glands
what components and glandular organs are associated with the foregut?
- stomach
- liver
- gall bladder
- pancreas
What are the components of the midgut (small intestine)?
- duodenum
- jejunum
- ilium
What are the components of the midgut/hindgut?
- caecum - mid
- ascending colon - mid
- transverse colon - mid/hind
- descending colon - hind
- rectum - hind
What are the 4 major functions of the alimentary system?
- motility
- secretion
- digestion
- absorption
What is motility?
- the movements of the alimentary system that mid and circulate its contents and propels these along its length
What is secretion?
- associated glands secrete water and other substances into the tract
What is digestion?
- large ingested molecules are chemically degraded to produce smaller molecules that cab be absorbed across the wall of the tract
What is absorption?
- nutrient molecules absorbed by the GIT and enter the bloodstream
What are the 4 layers of the gastrointestinal tract?
- mucosa
- submucosa
- muscularis externa
- serosa (adventitia)
What’s contained within the mucosa?
- muscularis mucosa
- lamina propria
- epithelium
What’s contained within the muscularis externa?
- circular muscle
- longitudinal muscle
What are the other components of the GI tract layers?
- lumen
- villus
- lymph node
- submucosal plexus
- myenteric plexus
- glands in the submucosa
What is prehension?
- act of grasping
what is mastication?
- process by which food is crushed and ground down by the teeth
Describe the structure of the oesophagus
- lined by stratified squamous epithelia
- longitudinally arranged smooth muscle of the muscularis mucosae varies in amount from anterior to posterior
- muscularis externa is entirely skeletal muscle in ruminant with transmission in smooth muscle at different points in other species
- mucous or mixed glands present in the submucosa again species variation
Give 4 examples of salivary glands:
- parotid
- mandibular
- sublingual
- zygomatic
What components make up the simple stomach? (dog and cat)
- cardiac region
- fundus
- body
- pyloric region
= glandular mucosa
What is a composite simple stomach?
- stomach of the horse and pig
- possesses a small area of non-glandular mucosa as well as glandular mucosa
What is the composite complex stomach?
- found in ruminants
- 4 chambers
1. rumen
2. reticulum
= non glandular mucosa
3. omasum
4. abomasum = glandular mucosa
What does the muscular sac do?
- important role in mixing food with gastric juices and transferring it to the small intestine
What sphincters are present in the stomach?
- cardiac sphincter - opening
- pyloric sphincter - ending
What are gastric folds called and what do they do?
- gastric folds are called rugae and are prominent when stomach is empty, when stomach is distended rugae flatten out
What glands are found in the cardiac and pyloric regions and what do they do?
- mucous glands produce mucous which provides protective barrier for the mucosa against gastric juices
What glands are found in the fundic region and what do they do?
- parietal cells produce Hydrochloric acid
- chief cells - produce pepsinogen
What glands are present in the liver?
- lobed gland that has both exocrine and endocrine functions
What does the exocrine liver do?
- produces bile
What does the endocrine liver do?
- plays an important role in fat, carbohydrate and protein metabolism
What functions does the liver have in general/
- Storage of glycogen
- biotransformation - conversion of toxic substances into non toxic ones
- synthesis of blood components
What is the gall bladder?
- storage of bile
- bile = essential in the digestion of fats and eliminating worn out red blood cells and some toxins
- absent in the horse and small rodent
The Pancreas has both exocrine and endocrine functions what are these?
- exocrine = pancreatic juices
- endocrine = insulin, glucagon and somatostatin
What is the small intestine segmented in to ?
and what is its main function?
- Duodenum
- Jejunum
- Ileum
- main function = digestion and absorption
The mucosal surface of the SI is increased by the presence of what?
- mucosal surface is increased by the Prescence of circular folds called plicae circulares and intestinal villi
What is the structure of villi in carnivores and ruminants?
- ruminants = short and thick
- carnivores = long and slender
How is the brush border formed?
- formed by the columnar epithelial cells which possess microvilli = brush border
How are intestinal crypts formed? and what do they contain?
- formed by invaginations of the epithelium at the base of the villi
- contain glands that secrete intestinal juices
What are Peyer’s patches?
- lymph node aggregations present in the lamina propria and submucosa especially the ileum
- stop infection from entering the intestine
What is the main function of the hind/midgut?
- main function is absorption of water and ions, microbial degradation of organic material and compaction and expulsion of undigested material and microflora
Why is microbial digestion critical in hind gut fermenters?
- important for the energy supply of horse and small mammals
What is the mucosal surface like in the mid/hind gut?
- flat
- villi are absent
