Gastrointestinal Tract Flashcards
Where do the fleshy fibres of the central tendon of the diaphragm converge ?
at the central tendon
What type of muscle is the diaphragm ?
skeletal muscles
What are the 2 recesses of the diaphragm ?
the costomediastinal and the costodiaphragmatic recess
What are the attachments of the diaphragm ?
sternal
costal
vertebral
What is the sternal attachment of the diaphragm ?
the xiphoid process
What is the costal attachment of the diaphragm ?
lower 6 costal cartilages
What are the vertebral attachments of the diaphragm ?
the left and right crus and the lumbocostal arches
What are the parts of the diaphragm that arise from the vertebra known as ?
the right and left crus
Where does the right crus arise from ?
arises from L1-L3 and some fibres of the oesophageal opening
Where does the left crus arise from ?
arises from L1-L2
What are the types of lumbocostal arches ?
the median and lateral
What are the 3 diaphragmatic apertures ?
aortic , caval and oesophageal
What is the vertebral level of the aortic opening ?
T12
What is the vertebral level of the oesophageal opening ?
T10 - it passes through the right crus not the central tendon of the diaphragm ?
What is the vertebral level of the caval opening ?
T8- though the central tendon
What structures pass through the caval hiatus ?
Inferior vena cava
right phrenic nerve
What structures pass through the oesophageal hiatus ?
oesophagus
right and left Vagus
Left gastric artery and vein
What structures pass through the aortic hiatus ?
aorta
thoracic duct
azygous vein
sympathetic chain
What is the motor innervation of the diaphragm ?
c3,c4 and c5 anterior ramii that form the phrenic nerve
What is the sensory Innervation of the Diaphragm ?
Centrally- phrenic nerve
laterally- lower 5 intercostal nerves
What are the functions of the diaphragm ?
ventilation - pull down the central tendon to increase thoracic volume
What are the muscles of the anterior abdominal wall ?
rectus abdominis
external oblique
internal oblique
trasnversus abdominis
What runs deep to the transversus abdominis
the transvercalis fascia
What are the directions of the fibres of external oblique ?
Inferomedially
What are the directions of the fibres of the internal oblique ?
superomedially
What are the attachments of the rectus abdominis ?
attaches between the rib cage and the pubic bone
has 3 transverse tendinous bands that join to the linea alba
What are the attachments of external oblique ?
arises from the lower 8 ribs
and inserts into the linea alba , pubic bone , inguinal ligament and the iliac crest
What are the attachments of Internal oblique ?
Arises from below the pelvis and the ilia crest and inserts into the costal margin and linea alba
What are the attachments of the transversus abdominis ?
arises from the lower 6 ribs , lumbar fascia , iliac crest , inguinal ligament and inserts into the linea alba
What is the innervation of the muscles of anterior abdominal wall ?
T7-L1 intercostal nerves between internal oblique and transversus abdominis
What are the functions of the muscles of the anterior abdominal wall ?
trunk movements
abdominal pressure regulation
expiration
What is peritoneum ?
A lining tissue that covers the primitive gut cavity
What are the types of peritoneum ?
visceral and parietal
What is the parietal peritoneum ?
lines the inner abdominal body walls
What is the visceral peritoneum ?
covers the viscera of the abdomen
What is the peritoneal space ?
between the visceral and parietal peritoneum and is occupied by peritoneal fluid that lubricates the viscera
What are the functions of the peritoneum ?
fixes organs
provides mobility
immune system
What are the intraperitoneal organs ?
they are covered with visceral peritoneum in folds away from the anterior abdominal wall
the organ is covered in peritoneum anteriorly and posteriorly
What are the retroperitoneal organs ?
not associated with visceral peritoneum
only covered with parietal peritoneum on the nateiror surface
What are mesenteries ?
double layered fold of visceralperitoneum that suspend organs in the peritoneal space
What do the mesenteries do ?
they connect intraperitoneal organs as well as providing a pathway for NV bundles
What is the order that food travels within the GI tract ?
Duodenum Jejunum Ileum cecum Ascending colon transverse colon descending colon sigmoid colon rectum
What are the anatomical features of the stomach ?
Oesophagus Fundus greater curvature Pylorum Antrum the stomach is continuous with the duodenum inferiorly body
What are the features of the pancreas ?
Common bile duct Head body tail pancreatic duct near the duodenum
What are the 2 terminal branches of the abdominal aorta ?
the right and left common iliac arteries
What do the common iliac arteries divide into ?
the right and left external iliac arteries
What do the external iliac arteries divide into ?
the right and left internal iliac arteries
What are the 3 unpaired arteries to the gut ?
the superior mesenteric
the coeliac trunk
inferior mesenteric
Where is the coeliac trunk located ?
just below the diaphragm at T12
What are the 3 branches of the coeliac trunk ?
the hepatic branch
splenic branch
left gastric branch
What does the superior mesenteric artery do ?
arises below the coeliac trunk and supplies the midgut
What does the inferior mesenteric artery do ?
Arises at L3 and supplies the hindgut
What is the arterial supply to the genitourinary system >
Renal arteries -
testicular and ovarian arteries
What unites to form the common iliac veins ?
the external and internal iliac arteries
How is the inferior vena cava formed ?
the unison of the common iliac arteries
Where does the inferior vena cava go ?
the right atrium
What are the veins that return from the gut called ?
the portal veins
Where do the portal veins go ?
to the liver carrying deoxygenated nutrient rich blood
What drains the liver ?
hepatic veins
Where do the hepatic veins go ?
enter the inferior vena cava
What are the muscles of the posterior abdominal wall ?
Psoas major
iliacus
quadratus lamborum
What are the attachments of Psoas major ?
arises from the T12-L5 and attaches inferiorly to the femur
What are the actions of Psoas major ?
it flexes the hip
What are the attachments of Iliacus ?
It attaches to the internal surface of the pelvic bone and superiorly to the femur
What are the actions of Iliacus ?
it flexes the hip and the thighs
What are the actions of quadratus lamborum ?
It attaches to the 12th rib and to the transverse processes of L1-L5 and inferiorly to the iliolumbar ligament and iliac crest
What are the actions of quadratus lamborum ?
it is a rotator and stabiliser of the hip
What provides the parasympathetic supply to the abdominal viscera ?
the vagus
pelvic parasympathetic splanchnic nerves from S2,S3,S4
Where do the postganglionic parasympathetic fibres go ?
to the walls of the viscera near the intramural ganglia
What is the sympathetic supply to the gut ?
greater , lesser and least splanchnic nerves from the thoracic and lumbar sympathetic chains
Where do the sympathetic fibres go ?
thoracic splanchnic nerves synapse in the coeliac and superior mesenteric ganglia
lumbar splanchic nerves synapse in the inferior mesenteric ganglia
What does the thoracic splanchnic nerves supply ?
foregut and midgut
What do the lumbar splanchnic nerves supply ?
hindgut
What is the arterial supply to the stomach ?
coeliac trunk
What is the venous drainage of the stomach ?
hepatic portal vein
Which veins unite to form the vena cava ?
common iliac veins
What is the arterial supply to the pancreas ?
coeliac trunk and superior mesenteric artery
What type of organ is the pancreas ?
retroperitoneal
Which muscle does the ureter lie on ?
psoas major
Why is quadratus lamborum important for ventilation ?
it fixes the 12th rib in place
What are the 4 main functions of the gut?
Digestion and Absorption
Excretion
Defence
Communication
What are the two main groups of organs in the GI tract?
Alimentary canal (Coiled hollow tube) Accessory Digestive organs
What are the layers of the mucosa in the GI tract?
Epithelium
Lamina Propria
Muscularis Mucosa
What is found in the Lamina Propria?
Glands, Lymphatics, Capillary Plexus
What is found in the Submucosa?
Glands, Lymphatics
What is found in the Muscular externa?
Smooth muscle, inner circular, outer longitudinal, myenteric plexus
What is found in the Serosa?
Loose connective tissue or mesothelium
What is the order of the layers in the GI tract? (innermost to outermost)
Mucosa,
Submucosa,
Muscularis Externa
Serosa
What are the features of columnar epithelium?
Absorptive
Single Layer of cells
Secretory
Where are you likely to find columnar epithelium?
Gut epithelium and exocrine pancreas
What are the features of stratified squamous epithelium?
Flat and scale-like
Can be several cells thick
Protective
Which epithelium is found in the oesophagus?
Stratified squamous (non-keratinised) epithelium
What are the layers of the stomach?
Gastric pits
Gastric Glands
What do parietal cells in gastric glands do?
They secrete HCL and KCL (gastric acid)
They secrete the intrinsic factor
What other cells are there in gastric glands?
Mucous secreting cells
Chief cells
What do chief cells do?
Secrete pepsinogen, renin, lipase
What are the layers of the duodenum?
Villi
Crypts of Lieberkuhn (Mucosal glands)
Brunners Glands 6(in submucosal layer)
Myenteric Plexus
What is a crypt?
The ‘pit’ of a villi
What are paneth cells?
Found in the crypt, they secrete antimicrobial peptides and lysozymes.
What features does the large intestine have?
No villi
Many intestinal glands containing goblet cells and columnar cells
Lymphoid tissue in lamina propria
What s the function of the large intestine?
Absorption of water fat and salts
What are the accessory digestive organs?
Teeth, Salivary Glands Pancreas Liver Gall Bladder
What are accessory glands?
They are derived from epithelial tissue
Connected to epithelial surface through ducts
What are unicellular glands?
They are individual cells within an epithelium.
What are examples of unicellular glands?
Type II alveolar cells
Goblet Cells
What are multicellular glands?
Glands made up of more than one cell
What are examples of multicellular glands?
Tubular glands (Cells lie along ducts) Acinar Glands (cells in sac at end of duct) Compound tubulo-acinar
What is an example of a compound tubulo-acinar glands?
Submandibular
What is an example of a compound acinar gland?
Parotid
Which glands produce saliva?
Parotid
Submandibular
Sublingual
What does the parotid gland secrete?
Serous secretions
What does the submandibular gland secrete?
Mixed secretions (mainly serous)
What does the sublingual gland secrete?
Mixed secretions (mainly mucous)
What are the minor salivary glands?
They are small aggregates in submucosa of oral cavity. (NOT gingiva and hard palate)
What do the minor salivary glands secrete?
Mixed secretions (mainly mucous)
What are the uses of saliva?
It helps to form a food bolus
It moistens and lubricates
Aids digestion of food
What are myoeptihelial cells
They sit on top of the acinar cells. Their contraction stimulates ejection of saliva.
What do acinar cells do?
They produce primary saliva
What happens to primary saliva as it travels along the ducts?
It gets modified
What medications can decrease salivary production?
CNS depressants Decongestants Muscle Relaxants Antinauseants CV drugs
Which diseases can decrease salivary production?
Sjogren Syndrome Cystic Fibrosis Diabetes Mellitus Thryoid Disorders HIV
What other causes can decrease salivary production?
Radiation therapy
Malnutrition
Depression/Anxiety
Ageing
What affects saliva composition?
Flow rate
Diet
Individual Variation
Relative contribution of glands
What are the organs of the digestive system ?
alimentary canal and the accessory digestive organs
What are the 4 layers of the gut wall ?
mucosa
submucosa
muscularis externa
serosa
What is the mucosa ?
inner lining of the GI tract - it is made of 3 further layers
mucosal epithelium
lamina propria
muscularis mucosa
What does the mucosal epithelium do ?
varies with region and function - constains transporting cells as well as endocrine and exocrine cells
What is the lamina propria ?
capillary plexus , glands and lymphoid tissue
What is the muscualris mucosa ?
thin layer of smooth muscle - contraction increases surface area for absorption
What is the Submucosa ?
another layer of the GI wall
made of connective tissue
contains meissners plexus
glands and lymphatics
What is muscularis externa ?
2 layers of smooth muscle
inner circular layer
outer longitudinal layer
contains the myenteric plexus (auerbachs plexus) between the layer s
What is the serosa ?
the layer most distant from the lumen and is continuous with the peritoneum
it is loose connective tissue
What are the 2 types of epithelium found in the GI tract ?
stratified squamous
columnar epithelium
What is the function of stratified squamous epithelium ?
protection
What is the function of columnar epithelium ?
absorption
has invaginations that increase surface area
What are the features of the columnar epithelium ?
can have a brush border
secrete mucus and enzymes
exocrine function
Where does the oesophagus run from ?
the pharynx to the diaphragm - it pierces the diaphragm at t10
How does the oesophagus conduct food ?
by peristalsis
What is the purpose of keratinisation ?
protection
Is the oesophagus keratinised or not ?
not keratinised
In the oesophagus which Gi wall layer can you find glands ?
submucosa
What is the type of epithelium in the oesophagus ?
stratified squamous
non keratinised
How many layers of muscularis externa are there in the oesophagus ?
2
What type of epithelium lines the stomach ?
simple columnar
How many layers of muscularis externa are there in the stomach ?
3
What are gastric pits ?
indentations in the stomach which denote entrances to tubualkr gastric glands
What are the cells types found in the gastric glands ?
parietal cells
mucous secreting cells
chief cells
enteroendocrine APUD cells
What do parietal cells do ?
secrete HCL and KCL - gastric acid
secrete intrinsic factor
What are other cells in the gastric glands ?
Mucous secreting cells
Chief cells
Enteroebdocrine APUD cells
What do chief cells do ?
Secrete pepsinogen , renin , lipase
What are differences between the stomach and oesophagus ?
Simple columnar epithelium in stomach And stratified squamous epithelium in oesophagus
Glands in the stomach are in mucosa abs glands in oesophagus are in sub mucosa
3 layers of muscularis externa in stomach and 2 layers of muscularis externa in oesophagus
What are the 3 parts of the small intestine ?
Duodenum
Jejunum
Ileum
What is a landmark of the small intestine ?
Villi
What do villi do ?
Provide a larger Surface area for absorption
What are between the villi ?
Crypts of lieberkuhn
What do the crypts of lieberkuhn do ?
Extend to the muscularis mucosa and they are glands
Where are the crypts of lieberkuhn found ?
In the duodenum
What are brunners glands ?
Submucosal glands
Found in the duodenum
Produce alkaline mucous for neutralisation
Provide correct conditions for enzymes
What does the duodenum also contain ?
Auerbach And myenteric plexus
What epithelium covers villi ?
Simple columnar epithelium
What do goblet cells do ?
Secrete mucus
What does mucus do ?
Creates a micro environment
Important for defence
Lubrication
Movement of digested substances
What are microvilli ?
Provide a brush border on epithelial cells - increase surface are for absorption
Where do you find paneth cells ?
Reside at bottom of intestinal crypts
What do paneth cells secrete ?
Antimicrobial peptides such as cryptidins
Lysozyme And phospholipase A2
What are enterocytes ?
Simple columnar epithelial cells found in small intestine
What do enterocytes do ?
Migrate up the crypt and along the villus
What does the large intestine do ?
Caecum
Appendix
Colon
Rectum
What does the large intestine do ?
Frames internal abdomen
Involved in absorption of water ,
Fat and salts
What is NOT present in the large intestine ?
Villi
What does the large intestine contain ?
Crypts of lieberkuhn
Auerbach plexus
Myenteric plexus
Where are exocrine Glands derives from ?
Epithelial tissue
What are unicellular glands ?
Individual cells with an epithelium
Type II alveolar cells - secrete surfactant
Goblet cells
How do goblet cells secrete mucus ?
Merocrinic secretion Via exocytosis
What are the 3 types of multicellular glands ?
tubular glands
acinar glands
compound tubulo-acinar glands
What are tubular glands ?
cells lie along ducts and secrete along the ducts
they can be simple or compound ducts
What is a simple duct ?
single unbranched duct (intestinal glands)
What is a compound duct ?
branched duct (gastric glands)
What are acinar glands ?
cells that are in the sac at the end of the duct (shaped like a grape)
What are the 2 types of acinar glands ?
simple and compound
What are simple acinar glands ?
sebaceous glands
What are compound acinar glands ?
parotid gland
What is an example of a compund tubulo-acinar gland
submandibular gland
What type of secretions does the parotid gland secrete ?
serous secretions
What is the innervation of the parotid gland ?
glossopharyngeal nerve
Where does the parotid duct run ?
around the masseter and opens opposite the 2nd maxillary molar
What type of secretions does the submandibular gland have ?
mixed but mostly serous
Where is the deep lobe of the submandibular gland ?
wrapped around the free border of the mylohyoid
Where does the submandibular duct run ?
runs forward above mylohyoid and into the oral cavity beneath the tongue
duct opens lateral to the lingual frenulum
What type of secretions does the sublingual gland have ?
mixed but mostly mucous
Where is the sublingual gland located ?
anterior part of the floor of the mouth
between the oral mucosa and the mylohyoid
Where are the sublingual ducts ?
small ducts open along the sublingual fold
What are the minor salivary glands ?
600-1000
found in small aggregates in the oral cavity
except gingiva and the hard palate
mixed (mainly mucous)
What is located at the end of each mucous tubule ?
mucous demilune
What are the types of cells found in salivary glands ?
acinar and myoepithelial cells
What are myoepithelial cells ?
sit on top of the serous demilunes
have a contractile apparatus
contraction generates salivary ejection
What is the main excretory duct ?
lobes produce saliva which enters the oral cavity through the main excretory duct
What are excretory ducts ?
interlobular ducts transport saliva between lobes
What are striated ducts ?
within lobules (intralobular ducts)
What are intercalated ducts ?
connect acini with striated ducts (ionic modification)
What are acini ?
secretory end pieces that share a lumen
What extends the lumen of an acinus ?
intercellular canaliculi
What do intercellular canaliculli do ?
increase secretory surface area
What type of saliva do excretory ducts contain ?
modified saliva
Where are excretory ducts found ?
in the connective tissue septa
What is the type of epithelium in excretory ducts ?
pseudostratified columnar epithelium
Why do striated ducts have striations ?
membrane folds
What type of epithelium is in striated ducts ?
simple columnar epithelium
What is the main role of striated ducts ?
saliva modification - absorb electolytes to turn the saliva from isotonic to hypertonic
What is the lumen of the acinus continuous with ?
lumen of an intercalated duct
What is the epithelium in intercalated ducts ?
simple cuboidal epithelium
What is the flow of saliva through ducts ?
intercalated - striated- excretory - main duct
What are serous end pieces ?
acinus
What are mucous end pieces ?
alveolus
What shape is the serous acinus ?
spherical
What shape is the mucous alveolus ?
tubular shape
What type of nuclei do serous acinus have ?
large spherical
What type of nuclei do mucous alveolus have ?
compressed nuclei
Which end pieces have intercellular canaliculi ?
serous acinus
Which glands can you find serous demilunes ?
mixed glands - submandibular
How are myoepithelial cells joined ?
desmosomes
What is the main role of myoepithelial cells ?
expel primary saliva
maintain cell polarity and structural integrity of the acinus
tumour suppressor activity
What is the function of the oesophagus ?
transport food to the stomach
What is the function of the stomach ?
storage
mechanical disruption
chemical disruption
protection from pathogens and auto-digestion
What type pf pH is found in the small intestine ?
basic pH
What is the function of the large intestine ?
absorb water and electrolytes
What are the digestion processes that happen in the mouth ?
chemical digestion
mechanical digestion
use of lingual lipase
What happens in mechanical digestion ?
mastication mixes food with saliva to form a bolus
What happens in chemical digestion in the mouth ?
alpha amylase begins strarch digestion in the mouth
hydrolysis of sugars releases acid
when the pH reaches 2.5 gastric secretion stops and the salivary glands release bicarbonate which neutralises
What is the pH in the mouth ?
6.5-7.0
What is the role of lingual lipase ?
secreted by glands in the tongue into the mouth
begins the breakdown of triglycerides into fatty acids and glycerol
What does the stomach do besides storage ?
regulates the flow of chyme into the small intestine
What is the role of Hcl ?
destroys bacteria
What does the mucosa of the stomach generate and why ?
bicarbonate to protect it from auto-digestion
this neutralises the gastric acid found in the glands close to the stomach wall
What is the major part of the stomach called ?
fundus
Where does most digestion in the stomach take place ?
pyloric region
What is the other function of the stomach ?
the pyloric antrum regulates the flow of chyme into the small intestine
What does the stomach do in terms of absorption ?
It prevents malabsorption- eg of cellulose
What do the smooth muscle cells of the stomach show ?
electric syncytium
Where do gentle mixing waves travel ?
between smooth muscle cells there are
Approximately how long is the small intestine?
6-9 metres long
What are the parts of the small intestine?
Duodenum
Jejunum
Ileum
What is the approximate length of the duodenum
2.5m
What is the approximate length of the jejunum?
2.5m
What is the approximate length of the ileum?
3.5m
What are the functions of the small intestine?
Mechanical and Chemical digestion. Absorption of nutrients.
How does mechanical digestion work in the SI?
Weak peristalsis occurs.
What does pancreatic juice contain?
Proteases,
Lipases,
Amylase
Sodium Bicarbonate
What is the role of sodium bicarbonate in the small intestine?
Neutralizes the chyme
What regulates the pancreatic juice production?
The hormones: Cholecystokinin (CCK) and secretin
What are incretins?
They are hormones that stimulate decrease of blood glucose levels.
What is bile’s function in the SI?
IT acts as an emulsifier for fats.
What regulates the secretion of bile?
The hormone CCK
What is the role of goblet cells in the SI?
They secrete mucus for protection and lubrication
What regulates the secretion of mucus?
The hormone Vasoactive intestinal polypeptide (VIP)
What does lactase do?
Hydrolyses lactose –> Glucose + galactose
What does enterokinase do?
It partially hydrolyses pancreatic zymogen proteases to release the active enzyme.
What is the importance of tight junctions in the epithelium?
It means materials must enter through diffusion/active transport. Which gives control of what substances can enter.
What are the exocrine cells in the pancreas arranged as?
A raspberry shape of about 12 cells called acini.
They are arranged around a central lumen.
What is the function of acinar cells?
They produce inactive enzyme precursors
They can modify ionic composition of secretion
What do acinar cells synthesise?
Amylases
Protease
Lipases
Nucleases
What are the enzymes produced by acinar cells stored as?
Zymogens
What is the basolateral membrane?
The ‘base’ of the acinar ells that transports nutrients into the cell for synthesis of digestive enzymes.
What controls pancreatic exocrine secretion?
Neural (vagus) and endocrine controls
Where does CCK bind on the acinar cells?
They bind to the basolateral membrane of acinar cells.
When is secretin secreted?
Response to acid in duodenum
What does secretin do?
Causes secretion of bicarbonate from pancreas after binding to the receptor on the basolateral membrane.
How are proteases secreted by the pancreas?
In secretory vesicles as inactive proenzymes (trypsinogen and chymotrypsinogen)
What is the role of enteropeptidase?
It cleaves inactive proteases into their active forms
What enzyme digests phospholipids?
Phospholipase A2
Which part of the GI tract has the largest area?
Small intestine
Which part of the GI tract has the lowest pH?
Stomach
Which phase of digestion is insulin secretion stimulated?
Intestinal Phase
What is the major precursor of the bile acids?
Cholesterol
What is the definition of digestion?
Process in which ingested food is converted into a form which can enter the blood or lymph
What is the definition of absorption?
Process by which nutrient molecules are transported through the intestinal epithelial cells into the blood or lymph
What are our dietary carbohydrates?
Fibre (mostly cellulose)
Sugars
Starch
What two types of sugars of we eat?
Disaccarides
Monosacchairides
What two forms of starch do we consume?
Amylose
Amylopectin
Why is amylopectin different to amylose?
It is branched with higher molecular wight, containing α-1,4 and α1-6 linked glucose.
What does amylase do?
It hydrolyses α-1,4 glucose links.
What CANT amylase do?
Hydrolyse α-1,6 links
Hydrolyse α-1,4 links adjacent to branch points
Where does Carbohydrate digestion occur?
In the mouth and the duodenum
Why can’t CHO digestion occur in the stomach?
The acidic pH inhibits α-amylase.
What are oligosaccaridases?
They are enzymes that complete CHO digestion on the brush border of the duodenum and jejunum
What examples of oligosaccaridases are there?
Isomaltase
Maltase
Lactase
Sucrase
What does lactose hydrolyse to form?
Glucose and Galactose
What does maltase hydrolyse to form?
Maltotriose and Glucose
What mechanism absorbs Glucose and Galactose?
Active transport through ‘sodium glucose transporter 1’ (SGLT-1)
How is fructose absorbed?
By facilitated transport
What occurs in lactose intolerance?
Deficiency of lactase
Undigested lactose enters colon causing osmotic diarrhoea
Metabolised by colonic bacteria in colon causing flatulence
What causes glucose-galactose malabsorption syndrome?
A mutation of SGLT 1, only fructose can be given
Where is psoas major in relation to quadratus lamborum ?
psoas major is medial to quadratus lamborum
What do the abdominal muscles do in terms of abdominal opressure ?
they incease abdominal pressure and this raises the diaphragm
What are the 3 branches off the aortic arch ?
bracicoephalic
left common carotid
left sublclavian
How is the superior vena cava formed ?
the unison of the right and left braciocephalic veins
Where can you find the vagus nerve and what is its route ?
in the carotid sheath between the internal jugular and common carotid artery
it gives off the right recurrent laryngeal in the neck
the left recurrent laryngeal given off at the aorta and curls around the aorta to go back to the larynx
vagus is parasympathetic to the abdominal and thoracic viscera
What are the gentle mixing waves ?
every 15-25 seconds
turn the bolus into chyme
What are the more vigorous waves ?
moves chyme from the body towards the Pylorus
more efficinet mixing
What are the intense waves ?
near the pyloric region - open the sphincter and aquirt chyme into the duodenum
What does Hcl do ?
denatures protein molecules
transforms pepsinogen into pepsin
What is the fat digestion in the stomach ?
gastric lipase
What happens to protect the gastric mucosa ?
mucous secreting cells release mucus as a physical barrier and bicarbonate as a chemical barrier
What are th 2 reflexes that regulate GI secretions ?
long cephalic reflexes- vagus and braisntem - emotional reflexes
short cephalic reflexes- mediated through the ENS- regulation of motility and secretions
What re the 3 phases of gastric activity ?
cephalic phase
gastric phase
intestinal phase
What happens in the cephalic phase /
stomach getting ready
responds to sight,smell and the taste and thought of food
vagus stimulated which activates the Parasympathetic nervous system to increase gastric secretion and motility
What is the gastric phase ?
stomach working
respond to swallowed food and part digested protein
What are the receptors stimulated in the gastric phase ?
stretch receptros and chemoreceptors
What are the actions of the gastric phase ?
gastric secretions
gut motiltiy and vigorous peristalsis to continue
chyme released into the duodenum
What is the endocrine influence on the Gastric phase ?
Gastrin released in the gastric glands release gastrin which causes increased gastric secretion and churning
Enterochromaffin like cells -increase gastric acid production
Somatostatin - released from protons acts as the negative feedback signal to stop pepsin and acid release
What is the intestinal phase ?
duodenum responds to arriving chyme
What are the receptors in the intestinal phase ?
stretch receptors
slow down gastric activity and increase intestinal activity
signal the sympathetic system - slow down
What is the endocrine influence on the intestinal phase ?
Secretin - decreases stomach secretions
CCK- decreases stomach emptying
GIP- decreases stomach secretions and motility
Wheree is gastrin released from ?
G cells
What is the cycle that food triggers ?
food
leads to increased acid secretion via Gastrin via direct or indirect action on parietal cells or on histamine
increased pepsinogen
somatostatin release by protons
modulates the acid and pepsinogen release
Where does the small intestine end ?
at the ileocecal valv3e
What are the functions of the small intestine ?
chemical digestion
mechanical digestion
absoroption
What mechanical digestion takes place in the small intestine ?
weak peristalsis
chyme mixed with intestinal juices in segmetns as released from the stomach
What are the 4 hormones present in the small intestine ?
What is their role ?
gastrin GIP GLP-1 CCK inhibit gastric acid secretion and increse insulin
Where is secretin released from ?
s cells of the duodenum
Where is GIP produced and released ?
K cells of the duodenum and the jejunum
Wheere is CCK produced ?
enteroendocrine cells
What does CCK do ?
stimulate the release of digestive enzymes and bile from the panceas and teh gall baldder
hunger supressant
Where is GLP-1 produced ?
produced by intestinal enteroendocrine L cells
What are GIP and GLP-1 ?
incretins
What are incretins ?
stimulate insulin secretion from pancreatic beta cells
inhibit glucagon secretion from pancreatic alpha cells
decrease blood glucose levels
released at the start of the inteestinal phase and signal that food is about to enter the blood
What regualtes pancreatic juice production ?
CCK and secretin
Where is the brush border ?
on the apical membrane
What ar ethe brush border enzymes for carbohydrate digestion ?
sucrase isomaltase
lactase
What does sucrase isomaltase hydrolyse ?
sucrose into glucose and fructose
What does lactase hydrolyse ?
lactose into glucose and galactose
What do peptidases do ?
act on the small peptides from stomach digestion
What are the brush border proteases and what are their origin ?
chymotrypsin and trypsin
they are derived from pancreatic precursors chymotrypsinogen and trypsinogen
What is the role of enterokinase ?
cleaves the inactive pancreatic precursors into active enzymes
What is the purpose of pancreatic precursors ?
prevent auto digestion
Where does lipid and nucleic acid digestion take plave ?
in the lumen no the brush border
What are the functions of the large intestine ?
chemical digestion
mechanical digestion
faeces foramtion
absorption of water and electrolutes
What ar ethe 3 waves in the large intestine ?
hasustral churning
gastroilial reflex
gastrocolic reflex
What does haustral churning do ?
relaxed puches are filled with muscular contraction
What is the gastrolilal reflex ?
stomach full
gastrin relaxes the iliocecal sphincter
make room for more food
What is the gastrocolic reflex ?
stomach full
strong peristaltic waves move contents of the transverse colon into the rectum
Are any enzymes secreted in the large intestine ?
no
What is secreted in the large intestine ?
mucus by goblet cells
What do bacteria ferment in the large intestine ?
undigested carbohydrate - co2 and methane
undigested proteins - indoles
bilirubin metabolims
What vitamisn do bacteria produce in the colon ?
vitmain B and K
After how long is 90% of water reabsorbed from chyme ?
3-10 hours
What does faeces contain ?
dead epithelial cells
undigested food - cellulose and bacteri a
Which reflex moves faeces into the rectum ?
gastrocolic reflex
Which receptors signal in the gastrocolic reflex ?
stretch receptors
What happens in defecation ?
parasympathetic nerves contract muscles of rectum and relax the internal anal sphincter
How is the external anal sphincter controlled ?
voluntarily
What is the blood supply of the liver ?
hepatic artery from the abdominal aorta
portal vein - nutrient rich blood from the GI tract
How are hepatocytes arrnaged ?
hexagonally
What are the hepatocytes in contact with ?
bile canaliculi on one side and the blood stream on the other
What are between hepatocytes ?
vascular spaces called sinusoids
What are kupffer cells ?
phagocytic macrophages which attach to sinusoids and play a protective roole
What does a portal triad conssit of ?
hepatic artery
portal vein
bile duct
What are the functions of the liver ?
filtering of blood protein synthesis carb metabolsim lipid metabolsim secretion of bile
How can the liver remove hormones , drugs and active molecules from the blood ?
excretion into the bile
phagocytosis by kupfer cells
chemical alteration
How is ammonia produced in the liver ?
deamiantion by amino acids
What does the liver do with ammonia ?
convert it intp urea to be excreted into the urine
How is ammonia released from glutamate ?
deamination of glutamate into alpha ketoglutarate produced ammonium ions
glutamate dehydrogenase
How is ammonia turned into urea ?
in the urea cycle
What is the route for the production and release of bile ?
bile is made in the liver
secreted into the hepatic duct
joins the cystic duct from the gall baldder
enters the duodenum through the common bile duct which goes through the pancreas
What does bile act for fats ?
emulsifier
What hormone regulates bile production ?
CCK
Where are chylomicrons produced ?
in the intestinal mucosa
enoplasmic reticulum of enterocytes
Where are chylomicrons found ?
in the blood and the lymph
Where are newly formed chylomicrons secreted from ?
through the basolateral membrane
into lymphatic vessels to veins
What is the role of chylomicrons ?
transport fat from the intestine top the liver and the adipose tissue
What do chylomicrons consist of ?
95% TAG
5% cholesterol
Apo B48
What are chylomicrons recognised by ?
lipoprotein lipases on the lining of blood vessels
What happens in chylomicron breakdown ?
broken down into FFA- oxidiesed for energy
LDL
HDL - taken up by the liver
reminants - taken up by the liver
What is the bile production rate in the liver ?
250-1500 ml a day
What is bile pigment ?
bilirubin
Where is bilirubin formed ?
spleen
bone marrow
liver
What is bilirubin a derivative of ?
haem groups without iron
What does bilirubin combine with ?
glucorinic acid - conjugated bilirubin
What is conjugated bilirubin converted into ?
urobilogen
by intestinal bacteria
What is urobilogen absorbed by ?
intestine into the hepatic vein
What does bile consist of ?
bile acids and bile salts
detergents for fat ingestion
glucoronic acid
95% of bile acid is reabsorbed by?
ileum
What is the sphincter oddi ?
betwene the bile duct and thre duodenum
What is the pancreas an outgrowth from ?
duodenum
What are the 2 types of glands found in the pancreas ?
endocrine and exocrine glands
What is the arrangement of cells in the exocrine pancreas ?
arranged as raspberry like acini around a central lumen
compound acinar
Many lumens contact each other to form what ?
ductules - coalesce to form the pancreatic duct
What do acinar cells form from ?
invagination of embryonic endoderm
What do the acianr cells open into ?
pancreatic duct
What is the apical membrane orientated towards ?
lumen
What is the basolateral membrane orientated towards ?
blood stream
Which hydrolytic enzymes do acinar cells synthesisie ?
amylases
proteases
lipases
nucleases
What are enxymes usually sotred as in the exocrine acinar cells and how are they released ?
as zymogens
as secretory vesivles in the apical membrane
What does the basolaterla membrane contain ?
receptors which hormones bind to to regualte zymogen secretion from the secretory vesicles in the apical membrane
What is the neural control of the exocrine pancreas ?
vagus in anticipation of a meal
As chyme nters the duodenum what doe CCK do ?
circualtes to the basoalterla membrane of acinar cells and binds to a specific receptor
What is secretin released from ?
enteroendocrione cells
What is secretin reelase din repsonse to ?
acid in the duodenum
What does secretin do ?
activates the secretion of bicarbinate from the pancreas
as pH increases bicarbonate release is stopped
What is the secretin receptor on the basolaterla membrane of the acinar cells like n?
7 pass trans membrane structure
GPCR
How are proteases sotred in the exocrone pancreas ?
as zymogen sin the secretory vesicles in the apical membrane of the acianr cell s
What are tehe enzymes released from the exocrine pancreas ?
lipases
phospholipas A2
amylases
Where is bicarbiante relesed from in the oancres ?
epithelial cells in the pancreatic duct
What are the endocrine cells in the pancreas arranged as ?
isleets of langerhans
What are the hormones released from the endocrine opancreas and where from ?
alpha cells - glucagon
beta cells - insuklin
delta cells - somatostain - GHIH
What is vomiting controlled by ?
emetic centre in the chemoreceptor trigger zone in an area of the meduall oblangata
What is the process of vomiting ?
increaseed parasymapthetic acrtivity leads to increased salivation
retroperistalsis
increase in abdominal pressure and decrease in intrathoracic pressure
propel stomach contents into the oesophagus
What is the sympathetic resposne in vomiting ?
sweating and increased HR
What are the cell to cell junctions in the apical membrane ?
tight junctions
claudin and occludin
adaptor proteins which link to underlying actin- Z0-1 AND Z0-2
What are the cell0 cell junctions in the basolateral membrane ?
adherens junctions
E-cadherin
A AND BETA CATENIN
What is the gut assocaited lymphoid tissue ?
protects agaisnt antigens entering across the intestinal mucosal barrier
aggregates of lymphoid tissue
What are peyers patches ?
bumps of lymphoid tissue in mucosa of GI tract
macrophages , dendritic cells and B and T lymphocytes found within
What are M cells ?
microfold cells
What are the role of M cells ?
specialised epithelial cells that overly peyers patches
provide info about the contents of the gut lumen to the immune cells of the GALT
What does the apical surface of the M cells contain ?
clathrin coated pits with embedded receptors
What happens when antigens bind to the receptor ?
transcytosis to basolateral membrane
released to intestinal fluid macrophages and lymphocytes
trigger inflammatory response
What do M cells transport microbes by ?
endocytosis
phagocytosis
transocytosis
What do dendriticc cells do ?
convert T cells into T reg cells - release IL10
supresses unecessary immune response
Damage to the intestinal epithelium leads to what ?
epithelial cells release signalling molecules
inhibition of IL10
D and T cells produce IL and TNF
neutrophils undergo NETosis and Apoptosis
How does food poisoning occur with M cells ?
some bacteria have evolved receptors which bind to M cell receptors
bacteria transported acorss M cells
immune system react- diarrhoea and vomiting
Good intestinal bacteria ?
biotin
vitamin K
intestinal flora
Good bacteria generate which antomicrobial peptides ?
lysoxymes
lactoferrin
defensins
What are the 2 types of multicellular glands ?
acinar and tubular
What is the epithelium in the excretory duct ?
pseudostratified columnar epithelium
Which salivary duct has pseudostratified columnar epithelium ?
excretory duct
Which parts of the salivary duct has simple cuboidal epithelium ?
intercalated dcut
What are serous demilunes ?
mixture of mucous and serous cells
What nutrients are abosrbed by the stomach ?
water , drugs , electrolytes and alcohol
What are some proteins produced in the liver ?
lipoproteins
plasma proteins- albumin, fibrinogen, globulin,transferrin
In what form is pigment secreted int the bile ?
conjugated bilirubin
What are the gut defence mechanisms ?
taste and mouth fell vomiting gastric acid hydrolytic enzymes mucosal epithelial barrier GALT intestinal bacteria
What controls vomiting ?
the emetic centre in the chemoreceptor trigger zone in the medulla oblanagata
What initiates vomiting ?
chemoreceptors and the CNS
What is the parasympathetic contribution to vomiting ?
increased salivation
retroperistalsis
Describe the pressure changes in vomiting ?
abdominal muscles contract- increase in abdominal pressure
lowering of thoracic pressure
propels stomach contents into the oesophagus
What is the sympathetic response in vomiting ?
increased HR and sweating
What type of junctions are in the mucosal epithelial barrier ?
tight junctions
What is the role of the mucosal epithelial barrier ?
keeps the ECF around the apical and basolateral memebranes separate
prevents diffusion through fucntional domians
What is the compostion of fibre ?
beta 1-4 glycosidic links
cant be digested as dont have the necessary enzymes
What is the structure of amylose ?
linear polymer of alpha 1-4 glycosidic links
What is the structure of amylopectin ?
branched polymer with alpha 1-4 and alpha 1-6 glycosidic links
Where can you find alpha amylase ?
pancreatic juice and saliva
What does amylase hydrolyse and what cant it ?
hydrolyses alpha 1-4 links
cant hydrolyse alpha 1-6 links or alpha 1-4 linkks close to terminal branches
Starch digestion release what ?
maltose
maltotriose
alpha limit dextrins
What are alpha limit dextrins?
branched polymers of glucose 5-9 units long
formed due to the inability of amylase to hydrolyse alpha 1-4 links next to branch points
What happens to alpha limit dextrins in the mouth ?
they can be taken up by bacteria and used as an energy source
The length of time food is in the mouth detemrines what ?
how much maltose and maltotriose is released
they are carcinogenic
What carbohydrate digestion takes place in the stomach ?
none- acidic pH inhibits alpha amylase
What carbohydrate digestion takes place in the duodenum ?
pancreatic alpha mylase
digests remaining starch into maltose , maltotriose and alpha limit dextrins
Which is faster salivary alpha amylase or pancreatic alpha amylase ?
pancreatic alpha amylase
What is the role of oligosaccharidases ?
on the brush border
they further digest the maltose, maltotriose and the alpha limit dextrins
Where can you find oligosaccharidases ?
in the duodenum and the jejunum
What does isomalatase (alpha dextrinase) do ?
hydrolyse alpha 1-6 links that amylase csnt
What does maltase do ?
hydrolyse maltose and maltotriose into glucose
What does lactase do ?
hydrolyse lactose into glucose and galactose
What does sucrase do ?
hydrolyse sucrose into glucose and fructose
What are the end products of digestion with oligosaccharidases ?
monosaccahrides- glucose , fructose and galactose which can be absorbed by the duodenum and jejunum
Where does the absorption of monosaccahrides occur ?
duodenum and upper jejunum
How are glucose and galactose actively uptaken ?
by sodium-glucose transporter 1
What type of active transport does the sodium-glucose transporter use ?
secondary active transport
What creates the electrochemical gradient in sodium-glucose active transport ?
Na/K ATPase
basolateral membrane
How do glucose and galactose leave the epithelial cell ?
glucose transporter protein 2
How is the entry of galactose and glucose into the epithelial cell mediated ?
by the presence of sodium in the GI lumen
How does fructose enter and leave the intestinal epithelial cell ?
enters using facilitated diffusion - glucose transporter 5
exits using glucose transporter 2
What is sucrase-isolmaltase deficiency ?
low levels of sucrase and isomaltase in the brush border
intolereane to starch and sucrose
fructose and glucose are tolerated
What is glucose-galactose malabosprtion syndrome ?
mutation in SGLT-1
fructose can be given
What type of transport is SGLT?
secondary active trnasport
symport
What is the type of transport with GLUT proteins ?
facilitated diffusion
uniport
What are alpha limit dextrins hydrolysed by ?
isomaltase
How is pepsinogen converted to pepsin ?
by protons
How much protein does pepsin digest ?
15%
What is pro elastase ?
converted to elastase
digests serine in elastin
What are the peptidases ?
aminopeptidase
dipeptidase
dipetidyl aminopeptidase- cleaves a dipeptide from end of the dipeptide
How can small peptides be further hydrolysed ?
by peptidases in the cytosol
What is present on the apical membrane to provide gradients for peptide transport ?
Na/H transporters
What are the amino acid transport systems on the apical membrane ?
5 dependent on Na - active
2 are facilitated
7 in total
What are the amino acid transport systems on the basolateral membrane ?
5
3 are Na independent - efflux of amino acids into blood
2 are Na dependent - active
How do fat soluble vitamins diffuse ?
diffuse acorss the brush border membrane
Where is vit B12 absorbed ?
ileum
How is B12 found in foods ?
bound to proteins
What happens to b12 in the stomach ?
released and binds to R proteins - high affinity
What is intrinsic factor ?
vitamin b12 binding protein
secreted by gastric parietal cells
binds to B12 with less affinity than R proteins
What degrades the R - protein B12 complexes ?
pancreatic proteases
What happens to the B12 afte degradation from R proteins ?
binds to IF- resist protease degradation
What does the brush border of the ileum contain ?
receptors for B12- IF complexes
What might happen in pancreatic insuffficinecy ?
no degradation from R proteins
B12 deficiency might occur
What is the B12 carrier ?
transcobalamine II
What inhibits gastric emptying locally ?
CCK - lipid present in the duodenum
What emulsifies lipids ?
bile salts and lecithin
What is the purpose of emulsification ?
increase the surface area for water soluble enzymes to act
What are the lipolytic enzymes found in pancreatic juice ?
pancreatic lipase
co-lipase
cholesterol esterase
phospholipase A
How is pancreatic lipase inhibited ?
bile salts bind to fat surface and prevent lipase binding
What does co lipase do ?
displaces bile salts on the fat surface enabling lipase to fucntion
What are the products of triglyceride break down ?
2-monoglyceride
2 x NEFA
What does cholesterol esterase do ?
cleaves a fatty acid from cholesterol esters
What does phospholipase A2 do ?
turns phsopholipids into lypophospholipid and NEFA
What is micelle formation ?
bile salts form micelles with the products of fat digestion
What do the bile salts act as in micell formation ?
surfactant
What is the structure of micelles ?
lipid molecules arranged in a spherical form
Where does absorption of lipids take place ?
in the ileum and the jejunum
What is the unstrirred layer ?
mucus layer
with microvilli between the lumen and the brush border
molecules pass through and become more disorgansied as they approach the apical membrane
What lipid transport occurs at the brush border membrane ?
cholesterol transporter mediates facilitated transport
microvilli membrane fatty acid binding protein transports long chain fatty acids by secondary active transport - Na/K ATPase
What is the role of cytosolic transport membrane ?
transport the products of lipid digestion to the smooth endoplasmic reticulum
What are the cytosolic lipid transport proteins ?
fatty acid binding protein and sterol carrier
What happens to lipids in the smooth endoplasmic reticulum ?
they are esterified again
enter pre chylomicrons
go to golgi
too large to leave across the basement membrane
lacteals - lymphatic capillaries- large enough - empty into the lymph and the the blood by the thoracic duct
Where does absorption of bile salts occur ?
in the terminal ileum
How are conjugated bile salts actively taken up ?
by an Na bile duct co transporter
How do bile salts enter the blood ?
they re enter the portal blood
bound to albumin
return to the liver
How does fructose get from the gut to the blood ?
enters via facilitated diffusion and then leaves bu GLUT 5
What are the brush border peptidases ?
aminopeptidase
dipeptidase
dipeptidyl aminopeptidase
Where does lipid break down occur in the GI tract ?
stomach
duodenum
jejunum
What 2 substances are responsible for emulsification ?
bile salts and lecithin
What is the role of R protein ?
to protect IF from gastric acid
Which compounds predominantly contribute to micelle formation ?
bile salts
What is the mechanism whereby lipids in the duodenum prevent gastric emptying ?
CCK
What are the functions of the kidney ?
Excretion
Homeostasis
Hormone production
What does the kidney excrete ?
foreign substances and products of metabolsim
urea
creatinine
hormones and drugs
What does the kidney regulate in homeostasis ?
ECF volume blood pressure osmolarity ion levels- calcium and potassium regulation of pH
What hormones does the kidney produce ?
renin
Urine produced by the kidney travels where ?
out of the kidney via the ureter and into the bladder where it is expelled by the urethra
Where does the renal vein drain back into ?
inferior vena cava
What are the 2 types of nephrons ?
Cortical nephrons- Superficial cortical and the midcortical
Juxtameduallry nephrons- penetrate deeply into the medulla and surrounded by the vase recta - a dense network of capilalries
loop of henle is longer in the juxtameduallry nephrons therefore th urine id more cocnentrated
What is the glomerulus ?
a cluster of blood vessels
water and solutes flter from the blood into the renal tubule through the glomerulus
What is the glomerulus bounded by ?
the afferent and the efferent arterioles
What is the purpose of the afferrent and the efferent arterioles ?
they contain smooth muscle which contracts to increase blood pressure
What is the nephron surrounded by ?
the peritubular capillaries
What happens in the renal corpuscle ?
the production of filtrate
What happens in the loop of henle ?
urinary concnetration
What happens in the distal tubule ?
control of water and Na balance
What happens in the collecting duct ?
control of water and sodium balacne
What is the average GFR ?
125 mL a min
180 L a day
What does the filter cocnsit of ?
fenestrated endothelium
collagen basement membrane
epithelium of bowmans capsule which has podocyte filtration slits
How does the filter restrict solute movement ?
based on size and charge
What is the first step in the production of urine ?
production of ultrafiltrate - contains no cellulr elements or proteins (RBCs and albumin)
The concentrations of solutes in the ultrafiltrate is similar to ?
the plasma
What is filtered out of the plasma ?
all plasma constituents except for RBCs and serum albumin
What is proteinuria ?
the presence of proteins in the urine as they are more readily filtered
What is haematuria ?
the presence of RBCs in the urine
What are the 3 pressures that determine the overall net pressure in the bowmans capsule ?
Hydrostatic pressure in the glomerular capillaries- outward
Hydrostatic pressure in the bowmans capsule - inwards
Colloid osmotic pressure gradient - inwards
What are the 2 mechanisms of autoregulation of the GFR ?
myogenic response
tubuloglomerular feedback
What is the myogenic response ?
arterial pressure increases the renal afferent arteriole is stretched and flow increases
vascular smooth muscle responds by contracting and thus increasing resistance
flow returns to normal
Where is the loop of henle situated between ?
the afferent and the efferent arterioles
What is communication between the tubules and the arterioles mediated by ?
Macula densa- plaque of epithelial cells adjacent to the arterioles in the tubules - they sense flow rate Granular cells (juxtaglomerular cells) in the afferent arteriole they secrete renin
What happens if there is an increase in GFR ?
Flow through the tubule increases
Flow past the macula densa increases
Paracrines are sent from the macula densa to the afferent arteriole
Afferent arteriole constricts and afferent arteriole pressure increases
Hydrostatic pressure in the glomerulus decreases
GFR decreases
How can we measure GFR ?
by using a substance that isnt excreted or absorbed into the tubules
What is inulin ?
a polymer of glucose that is not indogeneous
What is GFR and what is it measured in ?
rate of filtrate production
ml/min
What is the equation for GFR ?
Amount filtered=Amount excreted
Pinulin x GFR=V x Uinulin
What are the units for the plasma and the urine concentrations of the inulin ?
mg/ml
What is the unit for the rate of urine production ?
ml/min
What are the requirements for a substance to be able to measure GFR ?
must be freely filtered at the glomerulus
must not be abosrorbed or secreted into the nephron
Must not be subject to metabolsim or produced by the kidney
Must not alter the GFR
What are suitable substances for the measurement of GFR ?
Creatinine and Inulin
What is creatinine ?
product of skeletal muscle metabolism
Amount produced is proportional to the muscle mass
constantly produced therefore constantly excreted
What is the need for the GFR ?
allows us to assess the perfomrance of the kidney
see any signs of kidney disease
analyse the way the kidney handles solute
What is the clearance rate ?
mls of plasma totally cleared of a given solutein 1 minute
What is the equation for clearance rate ?
Px x Cx=Ux x V
If there is no reabsorption no secretion what is the relationship of the CR and the GFR ?
GFR=CR
eg. inulin
If there is total reabsorption and no secretion what is the relationship of the GFR and the CR ?
CR= 0
If there is net absorption what is the relationship between the GFR and the CR ?
GFR>CR
If there is net secretion what is the relationship between the GFR and the CR ?
CR>GFR
What affect does diabetes have on the urine ?
Excess plasma glucose means that more glucose is filtered out of the blood- not all of this can be reabsorbed therefore theire is glucose in the urine
increased osmolarity in the tubule meas that fluid is drawn in - triggers the thirst response and more urine is produced
What are the anatomical features of the kidney ?
renal artery renal vein urteter renal medulla and the renal cortex papilla
What is the journey through the oesophageal sphincter ?
Mouth pharynx and the larynx upper oesophageal sphincter oesophagus lower oesophageal sphincter stomach pyloric sphincter Dudoenum jejunum ileum ileocecal valve large intestine
What is dysphagia ?
difficulty swallowing
related to the oropharynx
leads to choking and unable to swallow
What is oesophageal stricture ?
narrowing of the oesophagus
lack of peristalsis
failure of the loweer oesophageal sphincter to relax
food stick to the oesophagus
What is gastroesophageal reflux disease ?
reflux of the gastric contenets through the lower oesophageal sphincter
intrinsic acids from the stomach can travel to the mouth and can damage enamel and the dentine
What is the laryngo-pharyngeal reflex ?
refluxate travels above the upper oesophageal sphincter
What is hiatus hernia ?
widening of the hiatus in the diaphragm
stomach enters the chest cavity
What is dydpepsia ?
indigestion
any food related pain in the upper abdomen
can be due to a gastric or duodenal peptic ulcer
can be caused by the H pylori bacteria
How can peptic ulcers lead to anaemia ?
perforation of the ulcers leads to anaemia
What is common treatment for Dyspepsia ?
antibiotics and PPI therapy
What is pernicious anaemia ?
Most common cause of vitamin B12 deficinecy
Autoimmune deficiency in which Gastric parietal cells which produce IF are destroyed
cant absorb b12 from the diet
leads to megaloblastic anaemia
treatement is b12 injections
What are some oral symptoms of pernicious anaemia ?
angular chellitis
atrophic glossitis- beefy tongue
What is coeliac disease ?
autoimmune response to gluten and Gliadin proteins
Causes damage to the villi which affects their ability to absorb
Intolerance to rye, wheat, oats and barley
What is Crohns disease ?
Inflammatory bowel disease
Causes are though to be genetic , environmental and an autoimmune response to commensal bacteria
can affect all GI areas and layers
What are the symptoms of Crohns disease ?
cobblestone effect in the ileum
mouth sores and ulcers
fistulae
anal fissures
What is diverticular disease ?
pockets created by the lining of the GI tract trapping food and becoming inflamed
due to muscular hypertrophy
What is IBS ?
disorder of the motor activity of the bowel
abdominal pain and altered bowel movement
diarrhoea and constipation
What is ulcerative colitis ?
inflmmatorry bowel disease
similar to crohns but more superficial
What is type 1 diabetes ?
autoimmune disease destroying pancreatic beta cells
requires lifelong insulin therapy
What is type 2 diabetes ?
Insulin resistance - insulin is produced and not recognised
body compensated by producing more insulin and eventually leads to insulin deficiency
Is the cortex or the medulla more densely supplied by the renal artery ?
cortex
How is urine concentrated ?
More water abosorption through the CD as it is permeable to water
increases the concentration inside the tubule and urine is hyperosmotic
Where is ADH produced ?
in the supraoptic and paraventricular nuclei of the thalamus
Where is ADH released from ?
posterior pituitary gland
What stimulates ADH release ?
increased plasma osmolarity
decreased blood pressure and blood volume
What are the actions of ADH ?
increases permeability of the CD
increases urea permeability of the CD
increases NaCl resbsorption in the TAL
What is the net effect of ADH ?
increases water absorption
What are changes in osmolarity detected by ?
osmoreceptors in the hypothalamus
Where do the osmoreceptors of the hypothalamus send a message to ?
posterior pituitary to release ADH
If there is an increase in plasma osmolarity ?
ADH secretion increases
How is ADH destroyed ?
liver and the kidneys
What is the cellular mechanism by which ADH increases water absorption ?
ADH binds to receptors on the basolateral membrane
stimulates the production cyclic AMP from ATP by adenylyl cyclase
activates protein kinse
insertion of AQP2 channels on the CD membrane - apical cell membrane
water permability increases and water is taken into the blood
If ADH is present what is the condition of urine ?
ADH increases water reabsorption from the CD therefore the urine is hyperosmotic
What happens if ADH is absent ?
there is no stimulation of the downstream aquaporin production therefore no water reabsorption and the urine is dilute
What is the the role of the supraoptic and paraventricular nuclei of the hypothalamus ?
stimulate ADH secretion from the posterior pituitary
What happens if there is a decreased ECF osmolarity ?
ADH release is supressed
thirst response is supressed
CD not permeable
What is the effect of ANP on ADH ?
ANP inhibits ADH
What is the affect of alcohol on ADH ?
alcohol inhibits ADH
What is the effect of nicotine on ADH ?
nicotie promotes ADH
What is the main role of aldosterone ?
Aldosterone is the main hormone regualting sodiium balance
Where is aldosterone released from ?
Zona Glomerulosa of the adrenal cortex
What stimulates aldosterone ?
hyperkalaemia
low blood pressure
angiotensin II in the RAS
What are the actions of aldosterone ?
increase potassium secretion into the DT and the CD
Increases sodium reabsorption in the DT and the CD
leads to increased blood volume and pressure
What is the cellular mechanism of aldosterone action ?
Aldosterone binds to receptors in the cytoplasm
initiates transcription of sodium channels
number of sodium channels on apical surface increases
increased sodium uptake
sodium goes through the basolateral membrane into the blood and inreases blood pressure
What are the 3 stimuli of aldosterone ?
Increased potassium
Decreased blood pressure
Decreased flow past the macula densa
What is the inhibitor of aldosterone release ?
Increased plasma osmolarity
What are the 3 components of the juxtaglomerular apparatus ?
Juxtglomerular cells
macula densa
extraglomerualr mesangial cells
Where do the extraglomerular mesangial cells sit ?
between the TAL and the afferent arteriole
What is the mode of activity in resposne to Sympathetic activity of the heart ?
high HR
to return to normal the wall tension in the afferent arterioles decreases
sodium delivery to the macula densa decreases
low blood volume
What does angiotensin II do to renin ?
it acts as a negative feedback loop and stops renin release
What is ANP ?
anti-natriuretic peptide
Where is ANP produced from ?
atria when stretched
What is the effect of ANP ?
increases water and sodium excretion
What affect does ANP have on the adrenal cortex ?
it stops aldosterone release
What affect does ANP have on the kidney ?
stops renin
increases GFR
inhibis sodium chloride and water reabsorption
What is the affect of aldosterone on the hypothalamus ?
stops ADH release from posterior pituitary
What is secreted into the proximal tubule ?
urea and creatinine
What is reabsorbed in the proximal tubule ?
Glucose
proteins
aminaoacids
lactate
What is reabsorbed from the descending limb ?
water
What is secreted into the loop of henle ?
urea
What is absorbed from the ascending limb ?
sodium and chloride
What is absorbed from the distal tubule ?
ions
What is secreted into the distal tubule ?
protons
ammonium ions
What is reabsorped from the collecting duct ?
water
urea
What percentage of water and solutes of the filtrate are reabsorbed into the PCT ?
70%
What is the average GFR ?
125 ml/min
What are the 3 layers of the glomerualr filter ?
Collagen basement membrane
fenestrated enothelium
epithelium of bowmans capsule with podocyte slits
How does the macula dens work ?
increased flow past the macual densa paracrine released from the macula densa and acts on the affferent arteriole increases resistance reduces hydrostatic pressure GFR reduces
What is the normal blood osmolarity ?
290 mOsmoles
What is the affect of nicotine on ADH production ?
inhibits ADH
What are the channels that Aldosterone promotes ?
ENACC channels
Na/K pump
What is reabsorbed i the proximal convuluted tubule ?
70% water and solutes
What is present on the apical surface of PCT ?
microvilli
What are the functions of the PCT ?
Reabsorption of the bulk of filtered NaCl
Reabsorption of glucsoe,amino acids
Secretion or organic molecules
pH homeostasis
What is the for, of Na+ transport on the apical membrane ?
Na transport acorss the apical membrane is mediated by glucose and amino acids in secondary active transport
counter exchange of Na/H exchanger
What is the form of Na transport in the basolateral membrane ?
Na is rmeoved by the Na/K ATPase on the basolateral membrnae
this is followed by chloride and water by a paracellualr route
What happens in the descending limb of the loop of henle ?
Water moves out
NaCl stays
What happens in the ascending limb of the loop of henle ?
Water stays
NaCl moves out
What are the mechanisms of Sodium transport in the loop of henle ?
Na/Cl/L transporter
Na/H transporter - allows the acidification of urine
Na/K ATPase on the basolateral membrane
What happens in the DCT ?
NaCl moves out the blood and H20 stays
What are the mechanisms of Na transport in the DCT ?
NaCl moves into the blood
Na/Cl transproter and then Na/K ATPase on the basoalterla membrane
What happens in the collecting duct ?
NaCl movemenrt
What are the 2 types of cells in the collecting duct ?
Principal cells
Intercalated cells
What do principal cells do ?
regulate ion balance based on expression of channels on the apical membrane
What are examples of the action of principal cells ?
aldosterone increases ENac Channels on the apical membrane
ADH increases aquaporins on the CD membrane
What are the actions of intercalated cells ?
Acid/base homeostasis
What are the two types of intercalated cells ?
Alpha and beta
What is the role of alpha intercalated cells ?
excrete protons into the urine and reabsorb bicarbonate into the blood
What channels does the alpha intercalated cells use ?
secrete protons by the H ATPase and H/K exchanger
Cl/HCO3 exchanger on the basolateral membrane
What is the role of beta intercalated cells ?
they excrete bicarbonate and reabsorb protons into the blood
What channels do the beta intercalated cells use ?
Cl/HCO3 exchanger
H ATPase
What happens after a high water load ?
water must be excreted in excess - dilute urine that is hyposmotic to the plasma
What is the normal plasma osmolarity ?
290 mOsml
What happens after a water restriction ?
water msut be retained
hyperosmotic urine to the plasma is produced
How is excretion of a dilute or concentrated urine achieved ?
by the countercurrent mechanism
What acts as the countercurrent multiplier ?
loop of henle
What acts as the countercurrnent exchanger ?
vasa recta
What does countercurrent flow mean ?
2 parallel limbs with fluid moving in opposite directions
What is the osmolarity of the PCT compared to the interstitial fluid ?
isotonic
What happens in the ascending limb of the loop of henle and what is the consequence ?
solutes move into the interstitium
increases the osmolarity of the interstitium
What happens in the descending limb of the loop of henle ?
fluid becomes more concentrated as water move out to equilibrate the interstitium
What happens as more fluid enters the loop of henle ?
more concentrated fluid is formed in the descending limb and enters the ascending limb
a gradient forms from top to bottom in the interstitium
What is the condition of the fluid at the bottom of the loop of henle ?
Hypertonic as water had moved out
What is the condition of the fluid at the DCT ?
hypotonic as solute has moved out
What are the vasa recta ?
long extensions of the peritubular capilaaries
run parallel to the loop of henle in juxtamedulalry nephrons
What are the functions of the vasa recta ?
water and solutes are reabsorbed by the vasa recta
provides o2 to the medulla
What happens in the descending vasa recta ?
solutes move into the VR down their conc gradient
water moves out the VR
What happens in the ascending vasa recta ?
water moves into the VR
Solutes move out the VR
What is the role of urea ?
important for maintaining medullary concentration gradient
What are the 3 mechanisms of pH control ?
buffers
respiratory control
renal control
What happens if the metabolic rate increases ?
co2 increases - equilibrium pushed to the right
increased protons cant be buffered by bicarbonate but can be buffered by non bicarb buffers such as Hb
bicarb is much higher now and can buffer protons from non resp sources
What is the consequence of increased protons in metabolism being released from organic acids ?
bicarbonate can act as a buffer
How is respiratory control of pH carried out ?
high levels of co2 signalled by the carotid and aortic peripheral chemoreceptors and they go to the respiratory centre and signal an increased VR
How is pH controlled in acidosis ?
H is high in the interstitial space reacts with bicarbonate to make co2 and water which dissociates into protons and bicarbonate and the protons are excreted by a H/K ATPase
alpha intercalated cells
How is pH controlled in alkalosis ?
beta intercalalted cells
carbon dioxide and water in the cell are reacted into protons and bicarbonate and the cl/HC03 exchanger excretes bicarbonate into the urine
What does contraction of the afferent arteriole lead to ?
reduces renal blood flow and reduces GFR and hydrostatic pressure
What does contraction of the efferent arteriole lead to ?
reduces RBF
increases hydrostatic pressire and increases GFR
What does dilation of the afferent arteriole lead to ?
increases RBF and increases GFR and hydrostatic pressure
What does dilation of the efferent arteriole lead to ?
increases RBF but decreases hydrostatic pressure and GFR
What does the macula densa do if therie is increases GFR ?
increased NaCl in the distal tubule
macual densa sense an increased flow
release paracrine that act on afferent arterioles
increases ressitance of the afferent arteriole and therefore reduce plasma flow
What are renal arterioles innervated by ?
sympathetic neurones
What are he sympathetic neurones activated in response to ?
fear
pain
response to fall in blood pressure
What does the sympathetic inenrvation cause ?
constriction of renal blood arterioles
