Anatomy Flashcards
Role of mouth and pharynx
to chop and lubricate food, starting carbohydrate digestion, delivering food to the oesophagus
Role of the oesophagus
to propel food to the stomach
Role of the stomach
Stores/churns food, continues carbohydrate digestion, initiates protein digestion, regulates delivery of chyme to duodenum
Role of small intestine
principle site of digestion and absorption of nutrients
Role of large intestine
Colon reabsorbs fluids and electrolytes, stores faecal matter before delivery to rectum
Role of rectum anal canal and anus
regulates expulsion of faeces
What are the accessory structures?
Salivary glands, the pancreas, the liver and gall bladder
What is the mucosa of the digestive tract?
the inner part of the wall, it is a mucous membrane containing epithelial cells, exocrine and endocrine glands
what is the submucosa?
thick later of loose connective tissue that surrounds the mucosa, it contains larger blood vessels, lymphatic vessels and the submucosa plexus (neurone network)
What is the muscular external?
it has an inner circular muscle layer and a longitudinal outer muscles layer, it contains the myenteric plexus which is a neutron network and is responsible for the segmental contractions and peristaltic movement in the GI tract
What is the serosa?
the outermost layer, made up of loose connective tissue
What are the four major functions of the alimentary canal?
Motility, secretion, digestion and absorption
What is meant by motility in the alimentary canal?
Mechanical activity mostly involving smooth muscle (skeletal at mouth, pharynx, upper oesophagus and external anal sphincter)
What is meant by secretion in the alimentary canal?
Into the lumen of the digestive tract from itself and accessory structures in response to the presence of food, hormonal and neural signals. Required for digestion, protection and lubrication.
What is meant by digestion in the alimentary canal?
The chemical breakdown of enzymatic hydrolysis of complex food to smaller absorbable units.
What is meant by absorption in the alimentary canal?
transfer of the absorbable products of digestion (with water, electrolytes and vitamins) from the digestive tract to the blood or lymph
What occurs to the lumen during circular muscle contraction
the lumen becomes narrower and longer
What occurs to the intestine during longitudinal muscle contractions
intestine become shorter and fatter
How does spontaneous electrical activity occur in the stomach, small and large intestines ?
It occurs as small waves
What does slow wave electrical activity determine?
the frequency, direction and velocity of rhythmic contractions
What cells control the electrical activity and where are they located?
ICC cells and they are located largely between the circular and longitudinal muscle layers but may be found elsewhere
What do ICCs form gap junctions with?
Each other and smooth muscle cells
What is needed for contraction to occur in the intestines?
The depolarising slow waves must have a sufficient amplitude to reach a threshold to trigger smooth muscle cell calcium potentials
what’s another name for slow waves?
Basic electrical rhythm
What determines whether slow wave amplitude reaches threshold?
neuronal stimuli, hormonal stimuli and mechanical stimuli
Excitatory effect that parasympathetic has on the GI tract
increased gastric, pancreatic and small intestinal secretion, blood flow and smooth muscle contraction
Inhibitory effect that parasympathetic has on the GI tract
relaxation of some sphincters, receptive relaxation of stomach
What is more important the sympathetic or parasympathetic?
parasympathetic
excitatory effects that sympathetic has on GI tract?
some sphincter contract
inhibitory effects sympathetic has on GI tract?
decreases motility, secretion, blood flow
what us the enteric nervous system?
the system of nerve cells located in the gut wall
What is peristalsis
Wave of relaxation followed by contraction that normally proceeds a short distance along the gut in an aboral direction
What is segmentation?
rhythmic contractions of the circular muscle layer that mix and divide luminal contents
where does segmentation occur?
the small and large intestine
What is colonic mass movement?
The powerful sweeping contraction that forces faeces into the rectum (occurs a couple times a day)
What is tonic contraction
sustained contractions
Where does low pressure tonic contraction occur?
organs with a major storage function such as stomach
where does high pressure tonic contraction occur?
sphincters
What are the six sphincters?
Upper eosophageal sphincter (UOS), lower oesophageal sphincter (LOS), Pyloric sphincter, Ileocaecal sphincter, the internal and external anal sphincters
What is the function of the upper oesophageal sphincter?
made up of skeletal muscle, relaxes to swallow and closes during inspiration to prevent air in stomach
What is the function of the pyloric sphincter?
regulates gastric emptying, usually prevents duodenal gastric reflux
What is the function of the ileocaecal sphincter?
regulates flow from ileum to caecum, distention of ileum it opens and distention of proximal colon is closes
What is the function of the internal and external anal sphincters?
are regulated by defaecation reflex
What are the three parts of the small intestine?
duodenum, jujunum and ileum
What are the three types of salivary glands?
parotid, submandibular and sublingual
What are the parts of the large intestine?
the appendix, caecum, the ascending colon, transverse colon, descending colon and sigmoid colon
What joint is used to open the mouth?
temporomandibular joint
what are the ‘closing’ muscles of the mouth?
masseter, temporalis and medial pterygoid
What is the ‘opening’ muscle of the mouth?
the lateral pterygoid
What nerve facilitates the opening of the mouth?
The mandibular division of the trigeminal nerve CN V3
What nerve supplies the posterior 1/3rd of the tongue?
glossopharyngeal
Is the posterior 1/3rd of the tongue in the oral cavity?
no
What direction does the posterior 1/3rd of the tongue face?
vertical
