Development and Organisation of the Alimentary System, Liver & Pancreas Flashcards
Accessory Organs of the gut
- salivary glands
- liver & gall bladders
- pancreas
Where do mouth parts develop from?
branchial arches
Where (other than the mouth) forms from the branchial arches?
- ear
- hand
- neck
Describe mesoderm
- middle developmental layer between the ectoderm and endoderm
- gives rise to the skeleton, muscle, heart and bones
What are indents in the branchial arches known as?
pharyngeal clefts or grooves
What are supplied by a cranial nerve in branchial arches?
cartilage and muscular components
How many pharyngeal arches are there in branchial arches?
6
How many clefts are there in branchial arches?
4
What develops from the first branchial arch?
- skin of jaw
- salivary glands
- tooth enamel
- buccal cavity
What develops from the 1st cleft of branchial arches?
- external components of middle ear
- tympanum
What develops from the 1st pouch of branchial arches?
auditory tube
What develops from the 2nd, 3rd and 4th branchial arches?
skin of the ear & neck
What develops from the 2nd pouch of branchial arches?
tonsils & lymphatics
What develops from the 3rd pouch of branchial arches?
thymus & thyroid
What develops from the 4th pouch of branchial arches?
thyroid
What 3 “parts” are in each branchial arches?
- nerves
- arteries
- cartilage
What does the gut develop as?
an endodermal tube
What surrounds the endoderm?
Splanchnic mesoderm
What forms muscle & connective tissue?
Splanchnic mesoderm
What provides nutrients to the embryo as the placental plate develops?
a yolk sac
At what week of embryo development do accessory organs appear?
week 6
What are the 4 layers of the gut wall?
- mucosa
- submucosa
- muscularis externa
- serosa
Describe mucosa
- lines the gut lumen
- has 3 layers
- has a thin ring of longitudinal smooth muscle
- contains mucus and electrolyte-secreting glands
-surface normally highly folded to increase digestive surface area
Describe submucosa
- thick layer of connective tissue
- provides structural support and elasticity
- contains submucosal nerve network
Describe muscularis externa
- has inner ring of circular smooth muscle
- has outer ring of longitudinal muscle
- contracts tube diameter
- constricts gut length
Describe serosa
- outer connective tissue layer
- secretes fluid to lubricate organs of the coelom
- attached to mesenteric membranes
What is the primary region of nutrient absorption?
the small intestine
What increases the absorptive area in the small intestine?
circular folds, villi, and microvilli
What are villus lined with?
epithelial cells and mucus-secreting cells
What is contained within villus?
- an arterial and venous circulation
- a lymphatic vessel
What is the lymphatic system prominent in?
lipid absorption
Describe the crypt of lieberkuhn
- site of enterocyte
- a site of water and mucus secretion
What is the primary function of the large intestine
water re-absorption and drying of feces
Where does the liver develop from?
ventral hepatic bud from foregut endoderm
What is the liver organized into?
units called lobules
What is each lobule in the liver fed by a branch of?
the hepatic artery and the portal vein
Where is bile stored?
the gall bladder
What is a sinusoid?
blood from the hepatic artery and portal vein that flows into the same capillary vasculature
Where does the alimentary tube develop from?
the cephalic and caudal parts of the embryo
Where does the pancreas develop from?
dorsal & ventral pancreatic buds
What is the pancreas organized into?
exocrine and endocrine structures
How is the exocrine pancreas organized?
as a series of glands along the pancreatic duct which drains into the duodenum
Describe duct cells in the exocrine pancreas
- exist at the base of each gland
- secrete bicarbonate
- the bicarbonate neutralizes digestive juices from the stomach
Describe acinar cells in the exocrine pancreas
- at the head of each gland
- secrete digestive enzymes into the duct
Where does the exocrine pancreas develop from?
the ventral pancreatic bud
Where does the endocrine pancreas develop from?
the dorsal pancreatic bud
What are islets of Langerhans in the endocrine pancreas?
a series of secretory islets perfused by a capillary network
What do islet cells do?
secrete metabolic hormones (insulin, glucagon and somatostatin)
