The digestive system Flashcards
What is the alimentary canal?
The continuous musclar tube running from mouth to anus
How long is the gastro intestinal tract?
5-7m
What is peristalsis?
The action that moves things through muscular tubes
Name component x:
Submucosal plexus (plexus of Meissner)
What is the submucosal plexus (plexus of Meissner)
A neural network located within the submucosa
What is component x?
Glands in the submucosa
What is component x?
The submucosa
What is component x?
Glands in mucosa
What is component x?
Lymphatic tissue
What is component x?
Lumen
What are components A, B & C?
A - Epithelium
B - Lamina Propria (areolar tissue)
C - Muscularis Mucosae
What is the serosa and what are its two components ?
Serous membrane (serosa) is smooth tissue membrane that secretes serous fluid. It consists of:
-Areolar connective tissue
-Epithelium
What is component x?
The myenteric plexus (Auerbach’s plexus)
What type of tissue is sub mucosa?
Dense irregular connective
What is component x?
Mesentery
Where is stratified squamous epithelium found within the alimentary canal?
-Mouth
-Oesophagus
-Oropharynx
-Anal canal
(because it is usually more protective)
What is interstitial fluid?
Fluid found in the spaces around cells. It comes from substances that leak out of blood. It helps bring oxygen and nutrients to cells and to remove waste products from them.
What happens to excess interstitial fluid around the cells?
It is drained away by lymphatic capillaries and into the lymphatic system to become lymph.
What does MALT stand for and why is it important?
Mucosa Associated Lymphoid Tissue
Reservoirs for the immune system. Once it has been introduced to a pathogen it remembers and retains it ready for the next encounter.
Where is the parotid salivary gland located?
In front of the ear
Where is the sublingual gland located?
Under the tongue (these glands produce around 70% of saliva)
Where is the submandibular gland?
Deep in the mouth, can be felt at the top of the neck.
Where is the uvula?
What are the gingivas?
The tissue around the base of the teeth (gums)
What are the labiums?
Lips
Where are the fauces?
Where are the frenulums?
What are vestibules?
Gap between the lips and cheeks, and the gums and teeth
At what point does the oesophagus enter the peritoneal cavity?
Level with the 10th thoracic vertebrae
What kind of muscular fibres are on the outer layer of the stomach?
Longitudinal fibres
What kind of muscular fibres are on the middle layer of the stomach?
Circular fibres
What kind of muscular fibres are on the inner layer of the stomach?
Oblique fibres
What are rugae?
Ridges formed inside the stomach
What are omenta?
Folds of peritoneum that connect the stomach to other viscera. Includes the lesser (double layer connecting the liver to the lesser curvature and duodenum) and greater (double layer spanning from the greater curvature to the transverse colon).
Where are mucous cells and what do they do?
A - They secrete mucous that protects the lining from acids, enzymes and abrasive materials
Where are parietal cells in the stomach lining and what do they do?
B - Responsible for gastric acid secretion (Including hydrochloric acid and intrinsic factor)
Where are chief cells in the stomach lining and what do they do?
C - The gastric chief cell (also known as a zymogenic cell or peptic cell) release proenzymes like pepsinogen and chymosin. Pepsinogen is activated into the digestive enzyme pepsin when it comes in contact with hydrochloric acid produced by gastric parietal cells.
Where are G cells in the stomach lining and what do they do?
D - G-cells are neuroendocrine cells responsible for the synthesis and secretion of gastrin, a peptide hormone that stimulates the parietal cells to secrete hydrochloric acid
What are the four main parts of the stomach?
-Cardia
-Fundus
-Body
-Pylorus
Describe the main functions of the stomach
-Bulk storage of undigested food
-Mechanical breakdown of food
-Production of hormones triggering gastric juice secretion
-Disruption of chemical bonds to make chyme
-Denaturing of pathogens
-Absorption of water, some lipid soluble drugs, and alcohol
-Production of intrinsic factor - required for vitamin B12 absorption
In order, what are the three sections of the small intestine?
-Duodenum (≈25cm)
-Jejunum (≈2.5m)
-Ileum (≈3.5m)
What are villi?
Tiny projections on the inner surface of the small intestine that help absorb digested food
What are the lymphatic vessels inside the villi called and what do they do?
Lacteal lymph vessels - they absorb fats and fat soluble vitamins
Where are intestinal glands located and what are their functions?
Intestinal glands, intestinal crypts or crypts of Lieberkühn lie at the base/in between villi. Responsible for absorbing water and electrolytes and secreting intestinal juice (Mucus, hormones (including serotonin) and digestive enzymes (including anti-microbial peptides.))
Intestinal juice is alkaline and helps buffer acids in the chyme
What type of acid is present in the stomach?
Hydrochloric
What is acute pancreatitis and what can cause it?
Sudden inflammation of the pancreas. Can be caused by:
- Gallstones in the common bile duct (choledocholithiasis)
-Heavy alcohol use
-Systemic disease
-Trauma
-In paeds, mumps
What is peritonisis?
Inflammation of the localised or generalised peritoneum.
What is ascites?
Abnormal buildup of fluid in the abdomen
Where does the pancreatic duct join to the duodenum?
Hepatopancreatic ampulla (Ampulla of Vater)
What is the largest gland in the body?
The liver, weighing roughly 1.5kg
What are the four lobes of the liver?
-The left lobe
-The right lobe
-The caudate lobe (posterior superior)
-The quadrate lobe (posterior inferior)
Where is the gall bladder in relation to the liver?
Posterior, inbetween the right and quadrate lobe.
What divides the left and right liver lobes?
The falciform ligament
What is the round (teres) ligament?
The free boarder of the falciform ligament, a remnant of the fetal umbilical vein
What duct extends from the gall bladder and how does it divide?
The cystic duct that splits into the common bile duct (inferior towards the pancreas) and the common hepatic duct (superior through the liver).
The common hepatic duct then splits into the left and right hepatic bile ducts
What carries blood away from the liver?
The hepatic vein
What blood supplies does the liver have and how do they differ?
The hepatic artery (25% of the blood supply, 50% of the oxygen supply ):
Delivers oxygenated blood straight from general circulation
The hepatic portal vein (75% of the blood supply, 50% of the oxygen supply):
Delivers mainly deoxygenated blood along with nutrients from the small intestine
What are sinusoids?
Blood vessels in the liver where oxygen rich hepatic arterial blood and nutrient rich hepatic venous blood mix and are conveyed to the hepatocytes before eventually draining into the central vain then the hepatic vein.
What are hepatic canaliculi?
Thin tubes in the liver that collect bile secreted by the hepatocytes
Where are kupffer cells located?
Bound to the sinusoidal endothelial cells, mainly near to portal areas
What do kupffer cells remove or ‘clean’ from the blood?
-Ingested bacterial pathogens
-Aged erythrocytes (preserving heme for re-use)
-Circulating hormones
-Debris
What do kupffer cells add to the blood?
-Antigens promoting either tolerance or T and B cell effector differentiation
-Cytokines (Affect the growth of immune and inflammatory cells) and chemokines (Stimulate the migration of cells, notably leukocytes)
What is kupffer cells’ role in liver scarring?
Some triggers, including carcinogenic agents, cause KC to initiate collagen production within the liver. Excess collagen inhibits liver function and regeneration.
What lies underneath the serosa in the GI tract?
Muscularis consisting of outer longitudinal muscle and inner circular muscle.
What is bilirubin?
A pigment produced from the breakdown of heme
What is the difference between unconjugated and conjugated bilirubin
Unconjugated bilirubin is not water soluble and binds to albumin to be carried to the liver.
How is bilirubin excreted or recycled?
It is conjugated then transported to bile. Bile in turn is converted to urobilinogen by intestinal bacteria and either secreted in stool or reabsorbed and transported back to the liver (99%) or excreted in urine (1%)
How does bilirubin cause jaundice?
In an unhealthy liver unconjugated bilirubin can remain in the blood tightly bound to albumin.
It is not filtered properly by the glomerulus and remains absent from the urine even as levels of it within the serum rise.
The body tries to expel it through the skin causing yellowing and intense itching (sometimes independent of each other)
What vitamins does the liver store?
Fat soluble vitamins: A, D, K & E
How does the liver respond to toxins?
Inactivates them
What is the livers relation to cholesterol?
It synthesises and releases it bound to transport proteins
How does the liver interact with iron?
It stores iron reserves
What nutrients does the liver interact with?
-Glycogen and lipids: storage of reserves
-Glucose, amino acids and fatty acids: maintenance of normal blood levels
-Other nutrients it synthesises and interconverts e.g. carbohydrates to lipids
What is the composition of bile?
Water
Ions
Bilirubin
Cholesterol
Bile salts
What is the largest blood reservoir in the body?
The liver
What do hepatocytes contribute to plasma?
Plasma proteins
What is angiotensinogen and where is it produced?
A hormone that helps regulate blood pressure. Produced in the liver
What is PUSHDoG?
Basic liver functions
Protein synthesis
Urea production
Storage
Hormone synthesis
Detoxification
Glucose and fat metabolism
What are the four sections if the large intestine?
Ascending, transverse, descending and sigmoid
What are the two flexures of the large intestine?
Right colic (hepatic) and left colic (splenic)
What is the cecum?
The pouch that forms the first part of the large intestine
What are teniae coli?
Three bands of longitudinal smooth muscle on the colon surface
What are epiploic appendages?
Small outpouchings of fat filled serosa covered structures on the external surface of the colon
What are haustra?
The pouch structures of the large intestine
What are diverticula?
Small bulges in the wall of the large intestine that form because of pressure
What is the difference between diverticular disease, diverticulitis and diverticulosis?
Diverticular disease is the presence of diverticula, diverticulosis is when it is asymptomatic, diverticulitis is when the diverticula became inflamed or infected
Which anal sphincter is innervated by the automonic nervous system?
The internal anal sphincter
Which anal sphincter is innervated by the somatic nervous system?
The external anal sphincter
Where is bile stored?
The gallbladder
Where is bile synthesised?
The liver
How does the gallbladder aid digestion?
When food is eaten it contracts and releases bile into the duodenum where it helps break down fats into fatty acids
What are common associated complications of peritonitis?
Can cause shock and Acute Respiratory Distress Syndrome (ARDS) and is very likely to cause sepsis if untreated.
How much fluid is normally in the peritoneal cavity?
50-75ml
What enzymes conjugate bilirubin?
(UDPGT) Enzymes convert unconjugated bilirubin to conjugated bilirubin (glucuronic acid) which is water soluble and can be transported into bile.
What are the main functions of bile?
The carry away waste and to breakdown fats
How does angiotensinogen regulate blood pressure?
By constricting blood vessels and triggering water and sodium intake.
Where are bile salts produced and reabsorbed?
Bile salts are produced by the liver and are to a large extent (>95% per cycle) absorbed in the terminal ileum, the final section of the small intestine.
What common anatomical differences can be present in the pancreas?
The pancreatic duct may exit directly into the duodenum or it may join with the common bile duct and then exit to the duodenum.
