Module 3: GIT & Renal Flashcards
what are the two types of digestion?
physical and chemical
what is peristalsis?
rhythmic waves that push food through the canal
what are sphincters?
close like drawstrings which open or close the tube when required
what are the accessory glands?
salivary, pancreas, liver and appendix
what is the fore-, mid- and hindgut?
foregut is from the oral cavity to the initial part of the duodenem
midgut is from the duodenem to the initial two-thirds of the transverse colon
hindgut is from the later one-third transverse colon to the upper portion of the anus
describe the function of the oral cavity
site for physical (teeth) and chemical (amylase) digestion. chemical digestion, saliva and amylase. and tongue is for taste buds and food bolus.
what is the function of the pharynx?
pharynx is a muscular tube in the throat that conducts air and food, protects your airway, vocals, immune function and swallowing reflex
three sections
1. above tip of soft palate is the nasal pharynx
2. everything between tip of soft palate and the tip of the epiglottis is the oropharynx
3. everything below tip of epiglottis and the start of esophagus is known as the hypopharynx or laryngopharynx
oesophagus?
a conducting pathway, also known as the food pipe, is a muscular tube that connects the throat (pharynx) to the stomach. primary function is to transport food and liquids from the mouth to the stomach for digestion.
stomach?
reservoir of 2.5L and is located in the upper abdomen. important functions are the gastric juice and smooth muscles help aid digestion.
what are the gastric juices that aid in digestion?
pepsin - hydrolyses proteins
liver?
size: approx 2kg, located in the upper abdomen with functions including bile production, storage, nutrient interconversion, detoxification, phagocytosis and synthesis
spleen?
acts as a filter for blood. recognises and removes old, malformed or damaged red blood cells.
pancreas?
located behind the stomach and adjacent to the small intestine. functions include:
1. endocrine function
- production of insulin, a hormone that lowers blood sugar levels
- production of glucagon, a hormone that raises blood sugar by prompting liver to release stored glucose into the bloodstream
- exocrine function
- pancreatic amylase: this enzyme helps break down carbohydrates into simple sugars like glucose
- trypsin and chymotrypsin: these enzymes assist in the digestion of proteins by breaking them down into smaller peptides and amino acids.
- lipase: responsible for the digestion of fats, breaking them down into fatty acids and glycerol. - bicarbonate production: produces bicarbonate that neutralises the acidic chyme coming from the stomach and maintains a proper pH environment for the functioning of digestive enzymes in the small intestine
what is the acini in the pancreas?
small clusters of cells found in the exocrine portion of the pancreas. acinar cells synthesise and secrete various digestive enzymes, including amylases, lipases, and proteases.
the duct system?
The digestive enzymes produced by the acini are collected and transported through a network of ducts within the pancreas. The main pancreatic duct, which runs through the centre of the pancreas, collects these enzymes and delivers them to the duodenum, the first part of the small intestine
Islets of Langerhans?
also known as pancreatic islets are micro structures found in the pancreas, which involves the regulation of blood sugar levels and various metabolic processes. these islets contain several types of specialised cells that produce and release hormones into the bloodstream:
- alpha cells
- beta cells
- delta cells
- pancreatic polypeptide cells
- epsilon cells
small intestine?
long coiled tube that connects the stomach to the large intestine. it is divided into 3 sections:
- duodenem: first and shortest segment that receives partially digested food from stomach along with digestive enzymes and bile from the pancreas and liver.
- jejunum: middle section of the SI, where most of the nutrient absorption takes place
- illeum: final and longest segment, continues the absorption of nutrients and is responsible for absorbing certain vitamins such as vitamin B12 and bile salts.
large intestine?
large intestine is divided into several sections, including the cecum, ascending colon, transverse colon, descending colon, sigmoid colon and the rectum. the appendix is attached to the cecum and has a role in immune function.
Functions:
1. Absorption of water and electrolytes: absorb water and electrolytes from the undigested food that enters from the small intestine.
2. Fermentation of undigested food: beneficial bacteria helps to ferment and break down substances that weren’t fully digested in the small intestine
3. Formation and storage of fecal material: contents of SI become solidified and form fecal material in LI
4. absorption of certain nutrients: LI absorbs some remaining nutrients and produce vitamins
5. elimination of waste: when the colon is full, it triggers the urge to have a bowel movement and the fecal material is expelled from the body through the rectum and anus
rectum and anus?
rectum: a chamber that begins at the end of the large intestine, immediately following the sigmoid colon and ends at the anus
Eventually, the descending colon becomes full, and stool passes into the rectum, causing an urge
to move the bowels (defecate)
anus - The anus is the opening at the far end of the digestive tract through which stool leaves the body
what does gastrointestinal system comprise of?
mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum and anus
what is upper GIT?
mouth, pharynx, esophagus and stomach
what is lower GIT?
small and large intestine, rectum and anus
where is the boundary between the upper and lower GIT?
ligament of trietz
layers of the GIT?
- mucosa
- epithelium
- lamina propria
- muscularis mucosa - submucosa
- blood vessels
- meissner’s plexus - muscularis mucosa
- myenteric plexus
- longitudinal muscle - adventitia
- connective tissue and variable amount of adipose tissue
ingestion?
the process by which food is taken into the alimentary canal. It involves chewing and
swallowing
propulsion?
movement of food through the GIT
segmentation?
occurs mainly in the small intestine, consists of
localized contractions of circular muscle of the GI tract
describe the anatomy of the oral cavity
mouth contains the vestibule and oral cavity proper and the palate
teeth has four types, incisors, canines, premolars, molars
- children have 20 teeth and adults have 32
tongue has taste buds, filiform, fungiform, foliate and cirumvallate
salivary glands: the parotid, submandibular and sublingual
taste pathways?
3 cranial nerves, the 7th, 9th and 10th cranial nerves
medulla, thalamus and gustatory centre in cerebral cortex
what controls salivary secretions?
two things control salivary secretions:
- local mechanism present in mouth: physical touching of food in mouth that cause production of saliva
- central control mechanism that enables to secrete saliva without eating it, see, smell food, body starts to salivate.
both mechanisms provide positive feedback to the medulla of the brain, autonomic nerves produce salivary glands
sympathetic: fight or flight (able to make dry mouth)
- sympathetic nervous system
- activation of beta receptors
- phophokinase A (enzyme) helps mobilise the calcium ions and vacuoles that are filled with mucus
- the vacuoles move toward basal side of the side and come into contact with the membrane. calcium helps them expel that mucoid content into your mouth and mucoid secretions that make the mouth feel dry
parasympathetic: rest and digest, secretes watery saliva
activates the alpha androgenic receptors and the muscarinic receptors.
alpha androgenic receptors use a neurotransmitter noradrenaline
muscarinic receptors use a neurotransmitter called acetylcholine
both receptors activate a common pathway, inositol triphosphate (IP3DAG)
IP3DAG has a dual action:
1. activate the calcium so the mucoid part is taken care of
2. phosphokinase C and starts to move chloride and moves into the lumen of the acinus of the salivary gland
chloride is moving and the cellular level (apicle side of cell) there is sodium, chloride and potassium moving (cotransporter)
describe the saliva process in the acinus and ducts
acinus of the salivary gland where production of watery saliva is isotonic, concentration is similar to plasma.
as we go through the ducts, there are specialised receptors that will pull all the sodium chloride out and balance it and push the potassium bicarbonate in. this part of salivary duct is not permeable to water, therefore does not follow sodium chloride out of cell.
the saliva is secreted into a main duct that is delivered into mouth to help with digestion.
what are the stomach’s cells?
the most important cell is the parietal cell, when food is being chewed in mouth, stomach is undergoing some physiological responses.
the cephalic phase is when the food is in your mouth and the stomach is getting ready to digest.
gastric phase of digestion is when food is physically activating the cells which are secreting the acid and pepsin to help to digest proteins.
proteins are digested and the food is moved into the duodenem where the intestinal phase of digestion occurs. there will be a negative feedback loop
what is retrograde peristalsis?
movement from the opposite direction of mouth to anus. for example, vomiting.
role of prostagladins for stomach?
protective for stomach, they control how much acid is being secreted and help find a balance between acid and mucus
acinus and ducts in the pancreas?
water is added through the duct system (NaHCO3) and NaCl is taken out and KHCO3 is put in
absorption in the large intestine?
when fecal matter comes into the large intestine, the sodium moves in and hydrogen moves out. the bicarbonate is not wanted in cell anymore because we want fecal matter to be alkaline, bicarbonate is moved out so chloride moves out. the sodium and chloride will join.
what are the components of a nephron?
a glomeruli and tubules
