Digestion

Question 1

Describe enzymes

Answer 1

A protein catalyst that increases the rate at which a chemical reaction proceeds, without the enzyme being permanently altered. Highly specific. Lipase breaks down lipids and protease breaks down proteins.

Question 2

What are accessory organs

Answer 2

Primarily glands that secrete fluids and enzymes into the tract. Salivary glands, pancreas, gall bladder, liver.

Question 3

List the main structures of the digestive system

Answer 3

Oral cavity with salivary glands. Pharynx (food, water or air). Oesophagus (just food). Stomach (churned into chyme). Small intestine (Duodenum, ilium and jejunum. Secretions from the gal bladder and pancreas that go into the duodenum). Large intestine (Cecum, Colon, Rectum, Anal gland). Anus.

Question 4

Approximately how long does it take for food to pass all the way through the digestive system

Answer 4

18 to 24 hours.

Question 5

What are the six functions of the digestive system

Answer 5

Ingestion, Mastication, Secretion, Digestion, Absorption, Elimination

Question 6

Describe ingestion

Answer 6

Introduction of food into the stomach via the mouth

Question 7

Describe mastication

Answer 7

Chewing. Chemical digestion requires large surface area so breaking down large particles mechanically facilitates chemical digestion.

Question 8

Describe secretion

Answer 8

Lubricate, liquify, digest.

Question 9

Describe digestion

Answer 9

Mechanical and chemical digestion of food into nutrients

Question 10

Describe absorption

Answer 10

Movement of nutrients out of digestive tract into cells.

Question 11

Describe elimination

Answer 11

Waste products removed from the body. Faeces, defecation.

Question 12

Explain the histology (wall) of the digestive tract

Answer 12

1- Mucosa: Innermost layer, secrets mucus. Epithelial cells.
2- Submucosa: Connective tissue layer. Contains blood vessels, nerves etc.
3- Muscularis: 2/3 muscle layers. Movement and secretion. Enable peristalsis.
4- Serosa/Adventitia: Outermost layer. Connective Tissue. Stability.

Question 13

Explain peritoneum in the abdominal cavity

Answer 13

Walls and organs are lined with serous membranes.
Visceral peritoneum: Covers organs
Parietal peritoneum: Covers interior surface of body wall.
Mesenteries: Peritoneum (epithelial tissue) which connects organs together. Routs for blood vessels and nerves.

Question 14

Explain the two omentums in the abdominal cavity

Answer 14

Greater omentum: Connects stomach to transverse column

Lesser omentum: Connects stomach to liver and diaphragm.

Question 15

What are the two sets of teeth

Answer 15

1- Primary/milk teeth. Develop in childhood.

2- Permanent/secondary teeth. Adult.

Question 16

List the four types of teeth and how many there are from front to back

Answer 16

8 incisors for cutting. 4 canine for tearing. 8 premolars and 12 molars for grinding.

Question 17

What are salivary glands and what is the role of saliva

Answer 17

Produce and secrete saliva into the oral cavity. Saliva protects the oral cavity, moistents, lubricates and helps to digest food.

Question 18

What is amylase and lysozyme.

Answer 18

Amylase: Enzyme found in saliva that breaks down carbohydrates into smaller sugar molecules.
Lysozyme: Antibacterial enzyme

Question 19

Describe the pharynx

Answer 19

AKA the throat. Connects the oral cavity to the oesophagus. Uvula (soft palate) that prevents food/drink from entering the nasal cavity.

Question 20

Describe the oesophagus

Answer 20

Tube that connects pharynx to the stomach. 25cm long. Lies posteriorly to the trachea. At the top is the epiglottis that prevents food/drink from entering the trachea.

Question 21

What are the three phases of swallowing

Answer 21

1- Voluntary phase
2- Pharyngeal phase
3- Oesophageal phase

Question 22

Describe the first phase of swallowing

Answer 22

Voluntary phase. Tongue pushes bolus to the back of the oral cavity towards the pharynx.

Question 23

Describe the second phase of swallowing

Answer 23

Pharyngeal phase. Uvula closes off the nasopharynx. Bolus touches receptors on oropharynx and swallowing reflex moves bolus down pharynx and into the oesophagus. Epiglottis covers trachea.

Question 24

Describe the third phase of swallowing

Answer 24

Oesophageal phase. Bolus is moved down oesophagus towards the stomach by peristalsis.

Question 25

Describe peristalsis

Answer 25

Process by which food moves through the gut. Waves of smooth muscle relaxations and contractions.

Question 26

What role does the stomach play in digestion

Answer 26

Food comes from the oesophagus and into the stomach which mixes and churns it into chyme (thick liquid). Produces mucus, hydrochloric acid and protein digetsing enzymes (e.g pepsin). Contains a thick mucus layer that lubricates and protects epithelial cells on stomach wall from acid pH 2-3.

Question 27

What is the gastroesophageal and pyloric opening

Answer 27

gastresophageal: Opening to the oesophagus
pyloric: Opening to the duodenum

Question 28

What are the four parts of the stomach

Answer 28

Cardiac, Fundus, Body and Pyloric

Question 29

What are the four layers of the stomach wall

Answer 29

1- Visceral peritoneum or serosa
2- Muscularis: Three layers. Outer longitudinal, middle circular inner oblique.
3- Submucosa
4- Mucosa

Question 30

What are rugae

Answer 30

Folds in the stomach wall that allow the stomach to stretch after eating (also increase surface area).

Question 31

Describe the movements of the stomach

Answer 31

3 muscle layers enable churning of food. Make chyme. Combination of mixing waves (80%) and peristaltic waves (20%). When mixing waves are happening both the oesophageal and pyloric sphincters are closed.

Question 32

Describe the small intestine

Answer 32

Large surface area for efficient absorption of nutrients and water. Three divisions: Duodenum (25 cm), Jejunum (2.5m) and ileum (3.5m).

Question 33

Describe the role of the first accessory organ of the duodenum

Answer 33

Liver/gal bladder. Bile is made in the liver and transported into the gal bladder. When eat a fatty meal, bile is secreted out of the gal bladder and down the common bile duct and into the duodenum. Role is to break down lipids and fats via the process of emulsification.

Question 34

Describe the role of the second accessory organ of the duodenum

Answer 34

Pancreas. Makes enzymes which travel through the pancreatic duct and into the duodenum. Will break down different macromolecules. Lipase (lipids), pancreatic amylase (carbohydrates) and trypsin (proteins).

Question 35

What is the role of folds in the small intestine

Answer 35

Increase surface area. Increases absorption and makes it more efficient.

Question 36

What are the three features that act to increase the surface are of the small intestine

Answer 36

Plicae Circulares: Circular folds in the wall of the small intestine
Villi: Folds of the mucosa that contain capillaries and lactaales.
Microvilli: Small folds on epithelial cell surface

Question 37

Describe the role of the large intestine in digestion

Answer 37

Absorption of water. Consists of cecum, colon (ascending, transverse, descending and sigmoid), rectum, anal canal. Bacteria/microbes synthesis vitamin B and K. Around 1500ml of chyme will enter cecum. 90% is reabsorbed (water). Other 80-150ml faces. Initiates the defecation reflex.