Digestion - Mace Flashcards
What are the accessory digestive organs?
Teeth, tongue, salivary glands, liver, gallbladder, pancreas
What’s the difference between accessory digestive organs and the GI Tract?
Accessory glands are called accessory because food does not pass through hem.
The GI tract consists of
Oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, anus
The boundary of the mucosa is?
Muscularis mucosa - this is the deepest layer of the mucosa.
The serosa is continuous with the?
Mesentary
What does the muscularis mucosa do? What does the mucularis externa do?
The muscularis mucosa is about assisting in glandular secretions, and it is part of the mucosa The muscularis externa is not part of the mucosa but its own layer, it consists of two layers - inner circular and outer longitudinal. This aids in churning, and peristalsis of food.
Name the layers of the GI tract
Mucosa —> submucosa —> muscularis externa —> serosa or adventitia.
Adventitia is in the?
Thorax, and also around the rectum and anus, covering of retroperitoneal parts in the abdomen.
Visceral peritoneum is located in? What is it made of?
Visceral peritoneum is made of serous membrane and is located in the abdominal cavity.
The enteric nervous system includes?
Submucosal nerve plexus Myenteric nerve plexus Can function independently of the CNS
What are 4 examples of the mesentary?
Greater momentum, mesentary proper, lesser omentum, mesocolon
The muscularis provides? What are the 2 different types of action that it performs.
Provides motility 1) peristalsis - wave of contraction, and relaxation, moves bolus of food from one place to another 2) Mixing=segmentation, started from the inner circular layer (establishes segmentation), mixing is continued inner circular layer contraction and then longitudinal layer also contracts. (Shortening and widening of the bolus of food).
What are the extrinsic salivary glands? What are they sensitive to? What are they influenced by?
Extrinsic salivary glands are parotid, sublingual, and submandibular glands. They are sensitive to touch, smell and tase, and can be influenced by the autonomic NS, PNS.
By volume the Partoid provides what % of our saliva? Submandibular?
Parotid provides about 25% Submandibular provides 65% Sublingual must provide 10% then.
What are intrinsic salivary glands? What are the 3 different ones.
These are salivary glands that secrete at a constant rate. They are single cells in the mucosal lining of the mouth. They consist of lingual, labial, buccal.
What type of secretion do the parotid glands create?
Clear, watery, serous fluid, rich in salivary amylase
What type of secretion do the submandibular glands make?
Some serous fluid with some mucus, more viscous than parotid secretion
What type of secretion do the sublingual glands produce?
Primarily thick, stringy mucus.
What are the three phases of deglutition? Which is voluntary vs involuntary?
Voluntary phase (voluntary)- bolus of food pushed by tongue against hard palate then moves towards the oropharynx Pharyngeal phase (involuntary) - as bolus moves into oropharynx the soft palate and uvula close off the nasopharynx, and the larynx elevates so that the epiglottis closes over laryngeal opening. Esophageal phase (involuntary) - Closure of the superior esophageal sphincter. Bolus moves down the esophagus via peristalsis. Bolus passes through the esophagus and enters the stomach. The inferior esophageal sphincter opens allowing the movement into the stomach.
What three layers of muscle does the stomach have?
Longitudinal layer, circular layer, oblique layer. Oblique layer is unique - allows it to twist
The gastric pits in the stomach are able to be evacuated by what muscle layer?
The muscularis mucosa
What are the deepest cells in the gastric pit? What is their function?
G - cells - Enteroendocrine cells that secrete gastric into the blood.
What do chief cells secrete?
Chief cells secrete pepsinogen. Pepsinogen turns into pepsin when it comes into contact with hydrochloric acid. They also secrete gastric lipase - this chops up lipids in the stomach but not a whole lot.
What do parietal cells secrete?
First it secretes intrinsic factor which isn’t utilized until the large intestine for vitamin b 12. They also secrete hydrochloric acid. And a lot of it. Takes stomach contents down to a pH of about 3.
What do mucous neck cells do?
They secrete acidic fluid containing mucin. These help protect the gastric pit from damage from the hydrochloric acid that is being secreted by the parietal cells.
What do surface mucous cells secrete?
They secrete mucin - like most goblet cells - but it also secretes an alkaline fluid
What does mucin need to combine with to form mucous?
Water
Describe the cephalic phase of gastric function.
Initiated by the thought, smell, sight, or taste of food (or even sounds of food preparation) 1) This is sensed by the special senses receptors in the higher brain regions. 2) This causes an increase in nerve signals relayed from the cerebral cortex and hypothalamus to the medulla oblongata. 3) The medulla oblongata integrates input from the higher brain centers and then sends a motor output signal. 4) The motor output signal goes to the stomach 5) These signals tell the stomach to both increase force of contraction but also the release of secretions.
Describe the gastric phase of the gastric function.
This is initiated by the presence of food in the stomach. 1) The receptors in the stomach are baroreceptors in the stomach wall. These detect stretch from the food in the stomach. There are also chemoreceptors that detect protein or high pH in the stomach contents. 2) Next sensory input from the receptors sends nerve signals relayed to the medulla oblongata. 3) Now the medulla oblongata integrates the sensory input from the stomach. It senses that there needs to be more action in the stomach. 4) So the medulla oblongata then sends increased nerve signals to the stomach. This is done along the vagus nerve. 5) The nerve signals from the medulla oblongata go to the stomach and cause both an increase in the force of contraction and a release of secretions. This works in a positive feedback loop. In addition: the presence of food in the stomach causes the release of gastrin. The gastrin targets both the stomach to increase force of contraction and also causes the release of secretions (especially HCL) and also stimulates the contraction of the pyloric sphincter. This works as an independent positive feedback loop.
Describe the intestinal phase of the gastric function.
This is initiated by the presence of acidic chyme in the small intestine. 1) Receptors: there are chemoreceptors in the intestinal wall that detects acidic chyme or low pH in the stomach contents. 2) the presence of the acidic chyme or low pH causes decreased nerve signals to the medulla oblongata 3) the medulla oblongata then integrates the information and decreases its nerve signals relayed to the stomach. 4) Decreased nerve signals are relayed from the medulla oblongata to the stomach. The effect being that the stomach is stimulated to both decrease force of contraction and release of secretions. In addition. Not only can you have acidic chyme in the duodenum, you can also have fatty chyme. Fatty chyme in the duodenum causes the release of CCK. CCK will also decrease the force of contraction in the stomach. Also acidic chyme causes the release of secretin. Secretin then also inhibits the release of stomach secretions.
Pesinogen is produced by __________ and activated by ______
Pepsinogen is produced by the chief cells and activated by hydrochloric acid secreted by the parietal cells.
What is the plicae circularis? What is on top of them?
The plicae circularis are the circular folds of small intestine in the GI tract. They are part of the submucosa
There are intestinal villi on top of the plicae circularis that are part of the mucosa.
What is the epithelial cell layer in the small intestine? What structure is located here as well?
The intestinal villi are composed of simple columnar epithelial cells. These have microvilli attached to them that helps absorb nutrients and increase surface area.
What are the different cells in the small intestine? (3)
Simple columnar epithelial cells Goblet cells - produce mucin Intestinal glands - unicellular and enteroendocrine cells
What are the two different intestinal glands in the small intestine and what do they secrete?
Unicellular gland cell - synthesizes enteropeptidase. Enteroendocrine cell - secretes hormones.
Where are the lacteals located in the small intestine? What is their function.
They are within the villi of the small intestine. They run with the blood vessels. They are responsible for absorbing the fats in the small intestine and they also help remove excess fluid from the villi themselves.
What are Brunner’s glands? What do they secrete?
They are specialized mucous-secreting glands that secrete a thick, alkaline mucus in response to certain stimuli Stimuli - low pH coming from the stomach.