Digestive System GIT - Canine Flashcards
In the digestive system, what are the organs grouped as?
grouped as alimentary canal and accessory organs
what is the alimentary canal?
it is a tube from lips to anus
what is the digestive system composed of?
mouth, pharynx, oesophagus, stomach, small and large intestine
what is the general structure of tubular organs?
have 4 layers
what are the four layers of the tubular organs of the digestive system?
tunica mucosa
tunica submucosa
tunica muscularis
tunica serosa/adventitia
what is the tunica mucosa?
it is the layer closest to the lumen (next to the lumen) and is protected by a layer of mucus
how many layers is the tunica mucosa divided into?
3
what is the tunica submucosa?
the layer found below the the tunica mucosa, it is dense connective tissue that may have glands, blood, lymph vessels and Meissner’s plexus (ANS)
What is the tunica muscularis?
smooth or skeletal muscle. contains the nerve plexus: myenteric (Auerbach’s) plexus (ANS)
What is the tunica serosa/adventitia?
loose connective tissue
What three layers is the tunica mucosa divided into?
the laminae epithelialis mucosa
lamina propria
lamina muscularis mucosae
What is the laminae epithelialis mucosa?
surface epithelium - for absorption and secretion, the type of epithelial cells depends on the function (where we are in the digestive system)
The cells are resting on a very thin basal membrane so that they are not floating around
what is the lamina propria?
layer of connective tissue (collagen, elastic and reticular fibres). Has mucosal glands, blood vessels and lymphoid structures and gut-associated lymphoid tissue
What is the lamina muscularis mucosae?
thin layers of smooth muscle
one layer of the three layers that make up the tunica mucosa is not always present, which layer is this?
the lamina muscularis mucosae
gut -associated lymphoid tissue?
lymphoid tissue that is specific to the gut
Describe the oesophagus:
it is relatively wide and dilatable
why can you sometimes not find the oesophagus in practicals?
because it has collapsed as there is no food in there
where is there constriction along the oesophagus?
at the origin
in all species the oesophagus is split into three parts, how many parts are there?
3
What are the parts of the oesophagus called?
cervical, thoracic and then abdominal
cervical part of the oesophagus?
follows the trachea down the neck and sits dorsally to the trachea (sits on top)
in which direction does the oesophagus incline before regaining a median position again?
left at first
what does the diaphragm separate?
The abdominal cavity and the thoracic cavity
after regaining a median, where does the oesophagus go?
has a continuous direction beyond trachea bifurcation (past the heart) and penetrates the diaphragm
where does the oesophagus join the stomach?
it joins the stomach ventral to the 11/12th thoracic verterbrae
what structure does the stomach have?
it is a C-shaped organ which has a tubular structure
what two sphincters are found in the stomach?
the cardiac sphincter and the pyloric sphincter
point of the muscles in the stomach?
protecting the stomach and the oesophagus e.g. no stomach acid gets sent in the wrong direction
where is the stomach found?
between the oesophagus and the small intestine
what side of the abdomen is the stomach found on?
left side
point of the sphincter muscles?
controls emptying the stomach
what are the several segments that the stomach is divided into? (from oral to aboral)
cardia, fundus, body and pylorus
what is the pylorus divided into?
the canal and the antrum
describe what the antrum and the canal are:
antrum is an entrance and the canal is what links the small intestine to the antrum (the canal gets smaller than the antrum)
what is the cardia segment of the stomach?
opening of the oesophagus
what is the fundus?
it is the blind expanded portion of the stomach
what is the middle segment of the stomach?
the body
what is distal to the body of the stomach?
the pylorus
what is the simple stomach primarily composed of?
glands
what part of the stomach do the glands mainly occupy and what type are these glands?
they are gastric glands and they occupy most of lamina propria
what do glands produce?
gastric juices
the fold in the stomach are called?
the rugae - created byntunica mucosa
what causes the ‘butterflies’ we get in our stomach?
the nerve plexus in the tunica submucosa
The nerve plexus is Meissner’s plexus
where are the folds present in the stomach?
in the mucosa of the stomach - in the tunica mucosa layer
What does the tunica muscularis consist of?
consists of three layers of smooth muscle between layers of the myenteric or Auerbacch’s plexus
What does the tunica submucosa contain?
Meissner’s plexuses
Name all of the gastric glands:
cardiac gland
fundic gland
pyloric gland
Where is the cardiac gland found in the stomach?
found in the cardiac region which occupies a very small area - this area contains mucous secreting glands and is closest to the oesophagus
Where is the fundic gland found in the stomach?
in the fundus region, which includes the space between the cardiac gland and pyloric gland regions
what are the fundic glands also known as?
the proper gastric glands
where are the pyloric glands found?
found in the pyloric gland region which is near the pylorus - it secretes mucus and the hormone gastrin
what is the collective name of the simple stomach glands?
collectively called gastric glands
describe the epithelium of the oesophagus:
stratified squamous epithelium
which cells line the lumen of the stomach?
simple columnar epithelium
what are found in the stomach wall?
many types of cells which are found in pits of the stomach wall
what are mucous cells?
mucous producing cells
what do parietal cells produce?
hydrochloric acid
what do chief cells produce?
protein secreting
what are the different gland cell types found in the simple stomach?
simple columnar epithelial cells
many types of cells found in pits in stomach wall
mucous cells
parietal cells
chief cells
endocrine cells
superficially, what does the gastric mucosa contain and what do these form?
contains gastric pits and these form superficial invaginations and are lined by mucus-secreting cells
where are simple columnar cells found in the stomach?
in areas with extremely high secretory or absorptive activity
which side of the stomach is the parietal surface?
the side of the stomach in contact with the liver
describe the membrane of the peritoneum:
thin serous membrane
layers of simple squamous epithelial cells supported by the pink connective tissue that is underlying structures in abdominal (and thoracic cavity but instead called *something else)
which side of the stomach is the visceral surface?
the side of the stomach in contact with the remaining abdominal viscera (remaining organs)
peritoneum?
connective tissue that lines abdominal and pelvic cavities and some of the organs around
what does the peritoneum consist of?
consists of parietal and visceral peritoneum (they are continuous with each other with connecting peritoneum)
what is connecting peritoneum?
double layered serosa connecting two peritoneum - mesentery - ligament - omenta - fold
what are peritoneal pouches?
excavations of peritoneum into the pelvic cavity
one point of serous membrane?
allow organs to move freely
omental bursar?
space between superficial layer of omentum and deep layer of omentum
two layers are freely moving because of the serous fluid
what is omentum?
it is connecting peritoneum
two types of omentum?
lesser and greater omentum
lesser omentum?
attached to lesser curvature of stomach to the liver
meaning of omentum in latin? hence the appearance?
apron - looks like an apron to the stomach
greater omentum?
attached to greater curvature of stomach, left part of the colon and left part of the pancreas
what two parts is the greater omentum divided into?
deep and superficial leaves (gap between these known as the omental bursa)
omental bursa?
potential space; area enclosed by greater omentum leaves
epiploic foramen?
natural opening into the omental bursa
omental bursa opening to peritoneal cavity
problem with epiploic foramen?
sometimes intestines move and get stuck in the epiploic foramen and the blood supply gets cut
blood vessels in the omentum - identifiable in practical:
dorsally caudal vena cava
ventrally portal vein
cranially caudate lobe of the liver
caudally hepatic a. (artery)
how many parts does the small intestine consist of?
3
name the parts of the small intestine:
the duodenum
jejunum
ileum
what occurs at the duodenum?
where the pancreas and bile ducts empty into the intestines
what is the beginning of the large intestine?
the cecum - the ileum joins onto here
messentry?
connecting peritoneum
it attaches to the abdominal wall opposite the second lumbar vertebrae by a short peritoneal attachment
what is that short peritoneal attachment?
root of the messentry
when suspended over the jejunum, what is the messentry called? etc.
mesojejunum etc. mesoduodenum, mesocolon
what is it called when the mesentery is suspended over the ileum and the cecum? (where they join)
ileocecal fold
describe the folding of the mucosa?
highly folded
what are the plicae circulares (circular folds)?
they are the transverse folds in the tunica mucosa and tunica submucosa
villi?
papillary projections
what are the villi lined with?
lined by columnar epithelial cells and some enterocytes
microvilli –>
form an apical brush border on the enterocytes
magnifies the surface 600x
forms a striated/brush border
crypts?
crypts of Lieberkuhn
between the villi, there are crypts which contain goblet cells and neuroendocrine cells
describe the structure of the duodenum:
longest villi of all three regions
tall columnar epithelial cells
highest number of goblet cells
crypt
tunica muscularis layer
length of villi in carnivores
tend to be longer
describe the structure of the ileum:
crypts
ileal mucosa contains large numbers of organised lymphoid tissue
describe the structure of the crypts in the ileum:
the epithelia of the villi extend down into the lamina propria where they form crypts
what are the important cells in the crypts in the ileum?
those involved in host defense and signalling (and stem cells)
what are peyer’s patches?
lymphoid follicles
three parts of the large intestine?
caecum
colon
rectum
caecum location?
lies on the right side of the median plane in the abdominal cavity
colon sections?
ascending, transverse and descending sections
what surrounds the crypts in the large intestine?
many goblet cells
on the left side - where does the stomach extend to and from?
extends to the 9th through to the 12th ribs
describe the positioning of the ascending duodenum on the left side:
travels cranially on the left side of the root of the mesentery
location of the jejunum on left side?
reaches from stomach to the pelvic inlet and greater omentum rests upon
at what veterbrae does the descending colon begin at?
begins at the level of the 12th thoracic vertebrae
explain the descending duodenum from the right side? (always on right side)
passess caudally on right side of abdomen, it’s a landmark
begins around 9th intercostal space and extends to 6th lumbar vertebrae
describe location of caecum?
right side
ventral to the right kidney and dorsal to the intestine
between 2nd and 4th lumbar vertebrae
where does the blood supply to the stomach come from?
comes from all three main branches of coeliac artery
what are the three main branches of the coeliac artery?
left gastric a.
hepatic a.
splenic a.
two types of hepatic atery?
right gastric hepatic a.
right gastric gastroepiploic a.
type of splenic artery?
left gastric gastroepiploic artery
veins in the stomach?
veins correspond to the arteries and drain to the portal vein
usually travel parallel to the arteries
blood supply to intestine?
cranial and caudal mesenteric arteries
(root of the mesentery contains the cranial mesenteric artery, hence it’s thick)
what is the coeliac artery a branch of?
the aorta
what nervous systems innervate the stomach and intestines?
the sympathetic, parasympathetic and enteric nervous system
what is the enteric nervous system?
part of the autonomic nervous system
autonomic nervous system?
involuntary, regulates motility.
how are the nerves arranged in the stomach/intestines? name the two plexuses:
mesh-like system of nerves
submucosal (MEISNER) plexus and Myenteric (AUERBACH) plexus
where is the submucosal plexus found?
(part of autonomic nervous system)
in submucosa
where is the myenteric plexus found?
(part of autonomic nervous system)
tunica muscularis
where would you make incisions in the stomach?
midline, the curvatures are well supplied with blood (well-vascularised)
What is the special name for the intestinal absorptive cells which are simple columnar epithelial cells?
enterocytes
The secretions of the Brunner’s gland
