LI anatomy and histology Flashcards
What is the function of the LI?
hindgut fermentation in some species
water absorption and ion balance
faeces produced
Describe the joining of the SI and LI
ileum joins at T-junction of caecum and colon
Horse: ileum goes into caecum which empties into colon
Fill in this table on the components of the GIT
What are the tunics of the SI and LI?
tunica mucosa
tunica submucosa
tunica muscularis
tunica serosa
Describe the histology of the LI
Simple mucosa:
- thinner than SI
- no villi
- no microvilli
- no enzymes as no digestion (small SA)
Mucous glands are long and straight
Goblet cells as chyme is drier so mucous is needed
GALT in mucosa and submucosa (lymphocytes and plasma cells)
Label the histology of the LI
Label the LI histology
Describe the blood supply to the large intestine
Cranial mesenteric artery - duodenum to descending colon
Caudal mesenteric artery - part of descending colon and most of rectum
Internal pudendal artery - caudal part of rectum
Veins run parallel to arteries and drain into hepatic portal vein (apart from veins of caudal rectum => caudal vena cava)
What is the clinical important of visceral larva migrans in horses?
lives in walls of cranial mesenteric artery affecting blood flow and autonomic supply to gut => spasmodic cholic
Describe the innervation of the intestines
Enteric nervous system
submucosa: Meissner’s plexus
Muscular layer: Auerbach’s plexus
Label the innervation of the intestine
What are the caecum and appendix?
Caecum is a large blind viscus in herbivores (small in carnivores)
The appendix is a narrow extension at tip of caecum (well-developed in rabbits, absent in carnivores)
What is the role of the caecum?
2 muscular valves for control of entry and exit of ingesta
Major site for microbial digestion of cellulose and absorption of water and electrolytes
Source of microorganisms for repopulating GI after illness
Describe the species differences of the caeca
Canine - short and spiralled
Feline - short, comma shaped
Bovine - small, no taenia or haustra
Pig - 3 taeniae (lateral, medial, ventral)
Horse - huge capactiy - base, body and blind-ending apex - 4 taeniae (medial, lateral, dorsal, ventral)
What are taenia and haustra?
Taenia: visible bands of smooth muscle and elastic fibres on external surface
Haustra: sacculation between taenia, not fixed
What are the valves in the equine caecum
Ileocaecal - base of caecum, raised as a papilla
Caecocolic - slit-like valve
Label the divisions of the large colon in cats and dogs
Describe the structure of the bovine colon
Long ascending colon with 2 sigmoid flexures and a double spiralled area
Short transverse colon
Straight descending colon (sigmoid flexure at end)
Label the bovine colon
Describe the anatomy of the suidae colon
cone-shaped and coiled ascending colon (base attached to left abdominal roof and apex points ventrally)
2 taenia and 2 rows of haustra
Coil inside a coil
Label the suidae colon
Label the equine large colon
Describe the equine large colon
Large ascending colon in 2 U-shapes on top of one another
Short transverse colon
Long descending colon
Describe the flow of ingesta through the equine ascending colon
right ventral
left ventral
left dorsal
right dorsal
