anatomy Flashcards
function of digestive system
2 roles: Digestion – function is to process food! Absorption – transfer of nutrients to circulation
gastrointestinal tract histology- mucosa
- The mucosa or mucous membrane lines the cavities of the body and surface of internal organs.
histology- laminate propria
-Lamina propria is a thin layer of loose connective tissue which lies beneath the epithelium. It contains inflammatory cells and provides support and nutrients to the overlying epithelium.
histology- muscular mucosae
Muscularis mucosae is the next layer deep to the lamina propria and is composed of smooth muscle and is continuous all the way through the entire length of the gastrointestinal tract.
histology- submucosa
Next is the submucosa which is deep to the muscularis mucosae. It is composed of dense irregular connective tissue and contains many blood vessels, nerves and also lymphatic vessels (which collects additional fluid aroud the body outside the vasculature).
histology- muscular propria
-The muscularis propria is also called the muscularis externa and comprised of inner circular muscle and outer longitudinal muscle. This muscle is smooth muscle and is responsible for peristalsis – movement of food and products of digestion.
histology- adventitia
-Adventitia is an outer layer of fibrous connective tissue surrounding an organ. In the gut, this would be at the oral cavity, upper end of the oesophagus in the chest, or thorax, and ascending and descending colon and rectum. A serosa would be that part of the tissue that is fixed, in other words the rest of the gastrointestinal tract. In addition, the serosa or serous membrane allows for reduction of friction.
miessners and auerbachs plexus
- nerve plexuses
- miessenrs: located in submucosa
- auerbachs plexus- between musuclaris and adventitia
brunners glands
secretes bicarbonate ions to neutralise the acid from the stomach
- found in submucosa
Peyer’s patches
- lymphoid follicles and form part of the immune function preventing the growth of dangerous bacteria.
- found in mucosa
oesophagus
Mucosa – stratified squamous (non-keratinising) epithelium (E), lamina propria, muscularis mucosae
Submucosa (SM) – glands (G) and lymphoid follicles (Ly)
Muscularis mucosae/externa (circular (CM) and longitudinal (LM)
Serosa
- upper 1/3: skeletal
- middle 1/3: mixed
- lower 1/3: smooth
layout abdomen
- R. hypochondrium
- Epigastric
- L. hypochondrium
- R. lumbar
- Umbilical
- L. lumbar
- R. iliac fossa
- Suprapubic (hypogastrium)
- L. iliac fossa
1 2 3
4. 5. 6
7. 8. 9
stomach
Found in left hypochondrium/
epigastric region
Anterior / superior
- Lower ribs/diaphragm
- Liver
Posterior / inferior
- Diaphragm, spleen, kidney (L.), adrenal gland, pancreas
Greater omentum (fatty tissue) attaches to greater curvature.
Pyloric stenosis can affect the pyloric sphincter.
Presents with projectile vomiting, without bile (as that enters the duodenum)
stomach histology
Stomach is a hollow muscular organ and is responsible for the breakdown of what is ingested by enzymes and hydrochloric acid.
It lies in the epigastrium and the left hypochondrium.
rugae, stomach histology
Rugae – folds of the organ which can be seen with the naked eye. They help increase surface area and allow for the folding of the organ.
3 layers of stomach wall
muscular propria/muscularis external
- These three layers of muscle help with the churning, or mixing, of the stomach contents called the chyme: usual inner circular and outer longitudinal, but also an extra layer called the innermost oblique.
endocrine cells
Endocrine cells produce gastrin
This stimulates the parietal cells to produce hydrochloric acid
The hydrochloric acid then breaks down pepsinogen to become pepsin produced from the chief cells.
Mucous and surface mucous cells protect the mucosa
small intestines
- simple columnar
- have finger like projections and are well designed to increase surface area, and therefore aid in the digestion and absorption which typically happens in the small intestine, namely the duodenum, jejunum and ileum.
duodenum
Receives chyme
Contains Brunner’s glands:
- alkaline secretion
Receives common bile duct
(Sphincter of Oddi)
- Major duodenal papilla
- Bile
- Pancreatic “juice”
Ends at duodenojejunal junction
serosa
- 2 layers of mesothelium
pancreas
functions: hormonal ( where the secretions pass to the blood stream), digestive (exocrine)
endocrine portion- islets of langerhans
insulin, endocrine
Insulin – promotes glucose absorption from blood into liver, skeletal muscle and fat cells. This enables the conversion to glycogen - i.e. storage of glucose in this form.
glucagon, endocrine
-this does the opposite and results in the conversion of the stored glycogen into glucose for release into the bloodstream when levels are low.
somatostatin, endocrine
this helps to reduce acid secretion and helps to slow down the digestive process, although it has a variety of other functions in the body.
exocrine gland
These digestive enzymes help break down carbohydrates, proteins and fats.
- bicarbonate ions
liver
The liver lies in the upper quadrant of the abdomen, extending over to the left. Specifically it lies in the right hypochondrium, extending to the epigastric region and then to the left hypochondrium.
It is the largest gland of the body and heaviest of our internal organs.
large intestine/colon
The colon is the distal part of the GI tract and extends from the caecum at the right iliac fossa to the anal canal.
caecum
Thecaecumis the most proximal part of the large intestine and is locatedbetween the ileum (distal small intestine) and the ascending colon. It simply acts as a reservoir for chyme which it receives from the ileum.
- can be found in theright iliac fossa of the abdomen. It lies inferiorly to the ileocecal junction and can be palpated if enlarged due to faeces, inflammation or malignancy.
ileocacaecal valve
Between the caecum and ilium is theileocaecal valve. This structure prevents reflux of large bowel contents into the ileum during peristalsis and is thought to function passively.
colon
The colon can be divided intofour parts– ascending, transverse, descending and sigmoid. These sections form an arch, which encircles the small intestine and is approx. 150cm long.
taenia coli
3 longitudinal bands of smooth muscle on the outside of the ascending, transverse and descending colon.
haustra
Circumferential contraction of the inner muscular layer of the colon
appendice epiploicae
Pouches of peritoneum filled with fat mainly on the transverse and sigmoid colon, though not the rectum.
goblet cells
Goblet cells – produce mucous as the role of the large intestine is to absorb fluid from the GI tract
blood supply for GI tract
Foregut – supplies the oesophagus (lower portion), stomach, liver, spleen and first half of the duodenum
Midgut – supplies the last half of the duodenum, jejunum, ileum, caecum, appendix, ascending colon and first half to first 2/3 of the transverse colon.
Hindgut – last 1/3 of the transverse colon, descending colon, sigmoid colon and rectum.
venous drainage of GI tract
Portal venous drainage is for the unpaired abdominal organs i.e. the gut and spleen.
Femoral veins drain the lower limb
Internal iliac veins drain the pelvis
Renal veins drain the kidneys
Hepatci vein is the main vein draining the liver
