Intestines, rectum and anus Flashcards
Name the 3 components of the small intestine, in order
Duodenum, jejunum, ileum
Name the 3 components of the large intestine, in order
Caecum, colon, rectum
Name the 4 functions of the intestines (hint if needed: movement, major site of ____, absorption of ___,___,___ and to _____/_____ residues)
- Movement of ingesta from stomach -> anus
- Major site of ingestion
- To absorb water, ions and products of digestion
- To concentrate and lubricate indigestible residues
What type of species would a caecum be relevant to digestion?
Herbivores or high plant material diets -> for fermentation
Name the parts of the duodenum (in order)
Cranial part, cranial flexure, descending duodenum, caudal flexure, ascending duodenum
Which part of the duodenum is most closely associated with the liver/ pancreas, receives bile and pancreatic ducts
Cranial flexure
The cranial flexure is attached to the liver via the ______
Hepatoduodenal ligament
What is the name of the flexure where the ascending duodenum/ jejunum merge?
Duodenojejunal flexure
What structure connects the ascending duodenum to the descending colon?
Duodenocolic fold of the mesentery
What structure is the longest in the small intestine?
Jejunum
What mesentery supports the jejunum?
Mesojejunal mesentery
Which artery, when combined with the mesenteries, forms the ‘root/ origin of the mesenteries’?
Cranial mesenteric a.
Is the junction between the ileum and jejunum well distinguished? ELABORATE
No, but can be defined by the presence of the antimesenteric ileal branch
what structure attaches the ileum to the caecum?
Ileocaecal fold
What structure does the ileum terminate at, and what structure does this lead into?
Ileal orifice -> caecocolic junction
What is the name of the sphincter located at the caecocolic junction?
Ileocolic sphincter
What is the function/ benefit of the ileocolic sphincter
Prevention of reflux of LI contents into ileum
At the pylorus, on a histology level, what structures disappear, and what appear
Pyloric glands disappear, crypts of lieberkuhn (intestinal glands) and duodenal glands (of Brunner), villi appear
How is absorption facilitated in the small intestine?
Increased surface area (by surface folds) and villi (lamina propria projections)
Name the layers of the GIT from the inside out
Tunica mucosa, tunica submucosa, tunica muscularis, tunica serosa/ adventitia
Name the 3 types of cells located within the epithelium of the tunica mucosa (of the GIT)
Enterocytes (absorptive cells), goblet cells, enteroendocrine cells
Describe the layer the enterocytes form in the tunica mucosa epithelium.
Enterocytes form an absorptive layer of simple columnar epithelium with a border of microvilli (in a protective coat of mucopolysaccharide - which contains glycocalyx, a digestive enzyme)
Describe the function of goblet cells.
Secrete mucin/ mucigen helping to form a barrier
Within the tunica mucosa, what is the layer of loose connective tissue containing elastic fibres.
Lamina propria
What material makes up the core of the villi, as well as fills in the spaces between them?
Lamina propria
What structures are located within the lamina propria
Crypts of lieberkuhn (intestinal glands), blood and lymph vessels, and lymphatic tissue
What vessel drains each villus?
Central lymph vessel (or ‘lacteal)
What are the nodules of lymphatic tissue called when located in the Ileum, and which layer/s are they located in (tunica ___)
Peyer’s patches -> may extend through the muscularis mucosa into the submucosa
The anti-mesenteric wall will always contain nodules called what?
Peyer’s pathches
Describe the epithelial cells overlying the peyer’s patches
Flattened, with long microvilli, no villi or glandular crypts
What are the 3 components in the tunica mucosa
Lamina propria, muscularis mucosae, epithelium
Within the muscularis mucosae (of the tunica mucosa), the circular muscle layer is _____, and the longitudinal layer is _____ (outer, inner).
Circular -> inner
Longitudinal -> outer
Brunner (duodenal glands):
Type of gland (secretion and structure)
Alkaline, mucoid gland
Simple, branched tubulo-acinar or alveolar glands
What is the prominent plexus located in the tunica submucosa
Meissner’s
What are the 2 main functions of the tunica muscularis layer?
To propel food caudally + to mix contents
A thin layer of connective tissue divides the inner circular layer and outer longitudinal layer (of the tunica muscularis), which plexus is located within here?
Myenteric (auerbach’s)
Describe the structure of the tunica serosa.
Simple squamous epithelia which overlies 3 layers of connective tissue (2 collagen layers sandwiching 1 layer of elastic fibres).
What structure joins the colon to the caecum?
Ileocaecal orifice
Name the 3 parts of the colon.
Ascending colon, transverse colon, descending colon
Is the small or large intestine absent of villi?
And do the number of goblet cells increase as you move caudal or cranial?
Do the crypts of lieberkuhn become deeper or more shallow as you move caudally from SI -> LI
Large intestine is absent of villi
Goblet cells increase as you move caudal
Crypts become deeper as you move caudal from SI -> LI
Name the 3 zones in the mucosa and submucosa region of the anus
Columnar, intermediate, cutaneous
Which zone are the anal glands located in, and which zone do they continue into?
Columnar zone, and continue into the intermediate zone
Name the 3 unpaired a.s that arise from the aorta in the abdomen, where each supplies part of the intestine.
Coliac, cranial mesenteric, caudal mesenteric
What organs are supplied by the cranial mesenteric a.?
Supplies intestine from distal duodenum -> transverse (middle) colon
What organs are supplied by the caudal mesenteric a.?
Supplies the descending colon ->proximal rectum
What a. supplies the distal rectum/ anus?
Internal pudendal a.
Describe the venous drainage from the intestines
The blood from the intestines flow through progressively larger veins -> hepatic portal vein -> liver
Lymph from the area supplied by the cranial mesenteric a. (say which area this is again) drains to what lymph node centre?
Area supplied by cranial mesenteric a.: distal duodenum -> transverse colon.
Drains to cranial mesenteric lymph centre
Lymph from the area supplied by the caudal mesenteric a. (say which area this is again) drains to what lymph node centre?
Area supplied by caudal mesenteric a.: descending colon -> proximal rectum
Lymph centre: Caudal mesenteric lymph centre
Where do efferent lymphatics drain to?
Intestinal or lumbar trunks
