Digestive System

Question 1

What are the 9 functions of the digestive system?

Answer 1

Food uptake (ingestion) 
Mechanical processing (chewing, etc) 
Digestion 
Absorption of nutrients, minerals & water 
Excretion 
Endocrine (eg. insulin, pancreas)
Immune (eg. tonsils)
Detoxification
Storage of nutrients (e.g. glucose) & regulation of their blood levels (liver

Question 2

What are the 4 tunics of the GI tract?

Answer 2

Mucosa, submucosa, muscularis, and serosa

Question 3

What is the peritoneum (including visceral peritoneum, parietal peritoneum, and peritoneal cavity).

Answer 3

The peritoneum is a serous membrane lining the abdominal cavity & organs. The visceral peritoneum covers organs. The parietal peritoneum covers the interior surface of the body wall. The peritoneal cavity is between the layers and is filled with serous fluid. The peritoneum is the largest serous membrane. The peritoneum is not smooth- it has lots of folds to make mesenteries.

Question 4

What are mesenteries and what is their function?

Answer 4

Unlike the pericardium, the peritoneum has lots of folds/extensions, called mesenteries. Mesenteries are two layers of peritoneum with a thin layer of loose connective tissue between. They hold organs to the abdominal cavity and are the routes by which vessels & nerves pass from the body wall to organs.

Question 5

What are retroperitoneal organs (give examples)?

Answer 5

Organs that lie against abdominal wall & have no mesenteries are retroperitoneal and are only covered by peritoneum on one side The kidneys & adrenals, pancreas, duodenum, rectum, bladder, ascending & descending colon are all retroperitoneal.

Question 6

Describe peritonitis.

Answer 6

Peritonitis is an acute inflammation of the peritoneal membranes, causing rubbing together of inflamed peritoneal surfaces which causes abdominal pain. This is due to irritation of the peritoneum due to escaped bile, bacteria from external due to a wound in the abdominal wall, or a ruptured appendix so bacteria enters the peritoneum. Peritonitis is life threatening.

Question 7

The abdominal wall is the boundaries of the abdominal cavity. It is made up common layers- describe them.

Answer 7

Deep = extraperitoneal fat, parietal peritoneum, & fascia
More Superficial on the anterior wall + layers of muscle
Superficial layers = superficial fascia & skin

Question 8

Describe hernias- what is it? What causes it? Where do they most commonly occur?

Answer 8

A hernia is a protrusion of an organ/fascia through the wall of the cavity that normally contains it. Hernias often arise when pressure is increased in the residing cavity. Hernias most commonly develop in the abdomen and as a weakness in the abdominal wall which evolves into a localised hole in the adipose tissue or abdominal organs covered in peritoneum can then protrude.

Question 9

Describe a hiatal hernia.

Answer 9

A hiatal hernia is when the stomach protrudes into the mediastinum through the esophageal opening in the diaphragm. It mostly has no symptoms but can cause pain from reflux gastric acid. It is often called the “great mimic” as the symptoms often resemble many disorders- for example, dull chest pain, shortness of breath, and heart palpitations.

Question 10

What forms the oral cavity?

Answer 10

cheeks, hard & soft palates & the tongue

Question 11

What are the functions of the tongue?

Answer 11

chewing, swallowing, taste, and speech

Question 12

What are the 2 types of muscle that make up the tongue?

Answer 12

Intrinsic muscles which have no attachment to
bones, and lie within tongue, giving the tongue shape,

and extrinsic muscle which anchor the tongue to
surrounding bones and move the tongue.

Question 13

What type of epithelium cover the tongue?

Answer 13

stratified squamous epithelium

Question 14

Mastication breaks food into smaller parts to _______ ________ _________ for digestion. The ______ and ______ bite/cut off food, while _____ teeth grind food. The mastication reflex is when chewing is stimulated by ______ _______. Signals from the brain provide ______ control to initiate or stop chewing or change the rate. There are ___ pairs of muscles which move the mandible/jaw bone.

Answer 14

Mastication breaks food into smaller parts to INCREASE SURFACE AREA for digestion. The INCISORS and CANINES bite/cut off food, while MOLAR teeth grind food. The mastication reflex is when chewing is stimulated by SENSORY RECEPTORS. Signals from the brain provide CONSCIOUS control to initiate or stop chewing or change the rate. There are 4 pairs of muscles which move the mandible/jaw bone.

Question 15

Lots of salivary glands are found throughout the oral cavity. 3 main pairs of salivary glands are located outside of the mouth & empty saliva into it. What are they?

Answer 15

the parotid gland which is the largest, anterior to the ear. It is a serous membrane, and produces watery saliva

the submandibular gland which is found below the mandible. It has serous & mucus membranes

the sublingual gland which is found below the tongue. It is the smallest, and is mostly mucus glands

Question 16

What is the function of saliva?

Answer 16

It prevents bacterial infection and allows lubrication. Saliva contains salivary amylase which breaks down starch so helps to form bolus for swallowing.

Question 17

Swallowing involves distinct phases moving food from mouth to pharynx to oesophagus. Describe the 3 phases of swallowing- voluntary, pharyngeal and esophageal

Answer 17

Voluntary Phase: The bolus of food is moved by the tongue from the oral cavity to the pharynx.

Pharyngeal Phase: This is a involuntary/reflex phase. It is controlled by the swallowing center in the medulla oblongata. The soft palate elevates, and the epiglottis tips posteriorly, which prevents food passing into the larynx. The pharyngeal constrictors allow a successive contraction from superior to inferior. The upper esophageal sphincter relaxes and the elevated pharynx opens the esophagus, and food is pushed into the oesophagus

Esophageal Phase: This is a reflex phase, which moves food into the stomach. There are peristaltic contractions of the esophagus, and the lower esophageal sphincter relaxes, allowing food to enter the stomach.

Question 18

The esophagus is a 25cm long ______ tube, which transports food from the ______ to the ______. It is collapsible. It is ______ to the vertebrae and posterior to the ______. It begins at the end of the laryngopharynx and passes through the esophageal hiatus of the diaphragm & ends at the stomach. It has a thick wall with ____tunics and ______ at the upper & lower ends. The mucosa is moist _________ ________ epithelium.

Answer 18

The esophagus is a 25cm long MUSCULAR tube, which transports food from the PHARYNX to the STOMACH. It is collapsible. It is ANTERIOR to the vertebrae and posterior to the TRACHEA. It begins at the end of the laryngopharynx and passes through the esophageal hiatus of the diaphragm & ends at the stomach. It has a thick wall with 4 tunics and SPHINCTERS at the upper & lower ends. The mucosa is moist STRATIFIED SQUAMOUS epithelium.

Question 19

Explain heartburn.

Answer 19

Heartburn occurs when the lower esophageal sphincter fails to close after food enters the stomach so the stomach contents can go back up to oesophagus. The acid from stomach can irritate the oesophagus & cause a burning sensation. This is treated with antacids to neutralize the acid. Heartburn is less problematic if you eat smaller amounts & don’t lie down after eating.

Question 20

Explain vomiting.

Answer 20

Vomiting is when there is forcible expulsion of stomach contents through the mouth. It is stimulated by irritation & distension of stomach. The stomach, diaphragm & abdominal walls all contract, and the esophageal sphincters open. It can lead to disturbed fluid balances if prolonged.

Question 21

What is this function of the stomach?

Answer 21

The stomach stores & mixes food. A meal is eaten more quickly than the small intestine can digest it, and so the stomach moves food into the small intestine at small intervals after eating. In the stomach there is very little absorption of nutrients, although glucose & some drugs can be absorbed.

Question 22

What are the 2 stomach openings?

Answer 22

The gastroesophageal (cardiac) opening from esophagus through cardiac sphincter, and the pyloric opening to the duodenum through the pyloric sphincter.

Question 23

What are the 4 parts of the stomach, and where are they?

Answer 23

Cardiac: near the esophageal opening

Fundus: left & superior to the cardiac part

Body: largest part, turns to right

Pyloric: narrow, antrum wider than canal, opens to the small intestine through the pyloric sphincter

Question 24

What are the layers of the stomach (outer to inner)?

Answer 24

• Serosa, which is visceral peritoneum
• Muscularis which has a further three layers
• Submucosa & Mucosa, which is folded into rugae when the stomach is empty, allowing the stomach lining to stretch

Question 25

The small intestine is narrow (~3cm) but long (~6m), and has three major segments- what are they?

Answer 25

* Duodenum (~25 cm) * Jejunum (~2.5 m) * Ileum (~3.5 m)

Question 26

What are the functions of the small intestine?

Answer 26

* It is a major site for digestion of food * Absorption of nutrients/vitamins * Removal of water from ingested fluids

Question 27

The _______ of the small intestine produces secretions- primarily _____ electrolytes, and _____. This _______ and ______ the small intestine wall from acidic chyme and digestive enzymes. Muscle in the muscularis ______ to mix & move chyme through the small intestine

Answer 27

The MUCOSA of the small intestine produces secretions- primarily WATER, electrolytes, and MUCUS. This LUBRICATES and PROTECTS the small intestine wall from acidic chyme and digestive enzymes. Muscle in the muscularis CONTRACTS to mix & move chyme through the small intestine

Question 28

How long does chyme take to pass from stomach to the large intestine?

Answer 28

3-5 hours

Question 29

The duodenum curves to the left- what sits in the curve?

Answer 29

The head of the pancreas

Question 30

What are the major & minor duodenal papillae?

Answer 30

They are found 2/3 of the way down the descending part of the duodenum, and are are openings to ducts from the liver & pancreas.

Question 31

The jejunum and ileum are similar in structure to the duodenum- what are the differences?

Answer 31

They have a decreased diameter and thickness of intestinal wall, & smaller number of folds & projections farther away from stomach.

Question 32

Which part of the small intestine is a major site of nutrient absorption?

Answer 32

Jejunum

Question 33

What are the lymph nodules in Ileum mucosa/submucosa which defend against microorganisms ingested called?

Answer 33

Peyer’s patches

Question 34

What is the illeoceal junction?

Answer 34

It is where the small intestine meets the large intestine. There is a sphincter & valve present to ensure one way flow.

Question 35

The liver is the largest internal organ and weighs around 1.4kg. Where is it found, and what are it's lobes?

Answer 35

It is found in the upper right abdomen, directly under the diaphragm, and is covered in visceral peritoneum. There are 4 lobes of the liver- the major right and left, and the minor caudate and quadrate. The right and left are separated by falciform ligament, which is a fold of peritoneum.

Question 36

What are the functions of the liver?

Answer 36

* Produce & secrete bile – 600-1000ml/day, which neutralizes and dilutes stomach acid & emulsifies fats * Storage of glycogen, fat, vitamins, copper and iron from blood * Removes worn out blood cells and other debris * Inter-converts nutrients – ingested nutrients are not always in form need; the liver can convert excess proteins & lipids from blood into what it needs * Detoxifies drugs/poisons/toxins

Question 37

What is the hepatic porta?

Answer 37

The hepatic porta is an area on the inferior surface of the liver. It is where the hepatic portal vein, hepatic artery, and hepatic nerve plexus enter the liver, and where lymphatic vessels and 2 hepatic ducts exit the liver.

Question 38

The liver has an ‘interesting’ blood supply. _______ artery carries _______ blood from the _____ to __________. The hepatic vein returns deoxygenated blood into the ____ _____. The hepatic portal vein carries _____ rich, _______ blood from the _______ to the liver before continuing to the heart & the rest of the body – this is important for removing _______.

Answer 38

The liver has an ‘interesting’ blood supply. HEPATIC artery carries OXYGENATED blood from the AORTA to HEPATOCYTES. The hepatic vein returns deoxygenated blood into the VENA CAVA. The hepatic portal vein carries NUTRIENT rich, DEOXYGENATED blood from the INTESTINE to the liver before continuing to the heart & the rest of the body – this is important for removing TOXINS.

Question 39

Describe liver disease.

Answer 39

Most mature hepatocytes can proliferate and replace the lost part of the liver. However, if the liver is severely damaged then hepatocytes don’t have enough “power” to replace lost parts, and a liver transplant is required.

Question 40

Describe hepatitis.

Answer 40

Hepatitis is an inflammation of the liver, caused by alcohol consumption of a virus. If it goes untreated, the hepatocytes die and are replaced by scar tissue, resulting in liver function loss.

Question 41

Describe liver ciarrhois.

Answer 41

Cirrhosis is when there is death of hepatocytes, which are replaced by fibrous tissue. The liver becomes firmer and paler in colour. A build up of fibrous tissue impedes blood flow through the liver. A loss of hepatocytes reduces liver function, resulting in jaundice due to a build up of bile. It can be caused by alcoholism, hepatitis, or nutrient deficiencies.

Question 42

What is the function of the gall bladder?

Answer 42

It stores around 50-70ml of bile from the liver. It also concentrates bile by absorbing water from it. After a meal the gall bladder contracts and bile exits into the duodenum.

Question 43

What causes gallstones, and when are they a problem?

Answer 43

Gallstones are formed when bile pigments and/or cholesterol from the liver precipitates in the gall bladder if their concentration is too high. If the stone is less than 1cm then you can have no symptoms. However, if it is larger it can block the cystic duct causing pain, nausea and jaundice. This can be due to excess cholesterol in the diet.

Question 44

What is the pancreas?

Answer 44

The pancreas is a large gland, with endocrine and exocrine functions.

Question 45

The pancreas has 3 parts- name each part.

Answer 45

the head, body, and tail.

Question 46

What is the endocrine function of the pancreas?

Answer 46

The endocrine function of the pancreas is carried out by the pancreatic islets which produce insulin to regulate blood glucose levels.

Question 47

What is the exoocrine function of the pancreas?

Answer 47

The exocrine function is carried out by acini cells which form lobules and secrete digestive enzymes (pancreatic juice) into the duodenum through the pancreatic duct. The pancreatic duct joins the common bile duct and enters the duodenum.

Question 48

Describe pancreatitis.

Answer 48

Pancreatitis is an inflammation due to pancreatic enzymes being released inside the pancreas and digesting itself. This can result from alcoholism, viral infection, pancreatic cancer, or cystic fibrosis. This results in abdominal pain and can lead to shock.

Question 49

The large intestine is _____ but shorter than the small intestine at around 1.5m. It has 6 major segments- the _______, _______ _______, ________ _______, _______ ______, _________ _______, and _______. Movement is sluggish through the large intestine, talking ______ hours. The large intestine converts _____ into ______ in the colon. This is through the absorption of _____/______ and secretion of _____ as well as the action of _______. Each day around 1500ml of chyme enters the cecum, with around ____% being reabsorbed, producing 80-150ml of feces.

Answer 49

The large intestine is WIDER but shorter than the small intestine at around 1.5m. It has 6 major segments- the CECUM, ASCENDING COLON, TRANSVERSE COLON, DESCENDING COLON, SIGMOID COLON, and RECTUM.. Movement is sluggish through the large intestine, talking 18-24 hours. The large intestine converts CHYME into FECES in the colon. This is through the absorption of WATER/SALTS and secretion of MUCUS, as well as the action of MICROORGANISMS. Each day around 1500ml of chyme enters the cecum, with around 90% being reabsorbed, producing 80-150ml of feces.

Question 50

What is the cecum? What is the vermiform appendix?

Answer 50

The cecum is a proximal blind sac where the small and large intestine meet at the ileocecal junction. It extends around 6cm inferiorly. The vermiform appendix is attached to the cecum. It is a small blind tube that contains numerous lymph nodules.

Question 51

The mucosa of the large intestine has no fold/villi unlike the small intestine. What does it have instead?

Answer 51

Instead, it has numerous straight, tubular glands called crypts.

Question 52

Describe the rectum.

Answer 52

The rectum is a straight muscular tube which connects the sigmoid colon to the anus. This is a thick muscular tunic compared with the rest of the digestive tract.

Question 53

What are the intraperitoneal and retroperitoneal segments of the large intestine?

Answer 53

The intraperiotoneal segments are the cecum/appendix, transverse colon, and sigmoid colon. The retroperitoneal segments are the ascending colon, descending colon, and rectum.

Question 54

What is the anal canal?

Answer 54

The anal canal is the last 2-3cm of the digestive tract, and ends at the anus. It is a very thick muscular tube which forms the internal anal sphincter.

Question 55

What are haemorrhoid, what are the symptoms, and how are they treated?

Answer 55

Haemorrhoids are a rectal vein enlargement or inflammation, which causes pain, bleeding, and itching, and is treated by changing diet or medication.

Question 56

What is appendicitis? What causes it? What are the symptoms? How is it treated?

Answer 56

Appendicitis is an inflammation of the vermiform appendix. This is usually due to an obstruction of the appendix. The secretions can’t pass so they accumulate, and the appendix swells. Symptoms include pain, nausea, loss of appetite, fever, vomiting, and diarrhea or constipation. Treatment is an appendectomy. If the appendix bursts the infection spreads throughout the peritoneal cavity, causing peritonitis.

Question 57

What are peptic ulcers?

Answer 57

Peptic ulcers are lesions in the lining of the stomach or small intestine, usually due to a bacterial infection.

Question 58

What is IBS?

Answer 58

IBS is a condition with unknown causes that results in constipation alternating with diarrhea. It has a high familial incidence.

Question 59

What is constipation?

Answer 59

Constipation is the slow movement of faeces through the large intestine so increased fluid absorption and faeces become hard and dry. This can be caused by irritation in the sigmoid colon, and is prevented by a high fiber diet.