U1T7 - Tissues & Organs

Question 1

What is the point of peristaltic contractions in the stomach?

Answer 1

Keep the chyme moving towards the duodenum.

Question 2

What does the pyloric sphincter do?

Answer 2

Controls passage of food into duodenum by alternately contracting and relaxing. It can hold back food or let it through.

Question 3

How long is the small intestine in humans? How much of it is duodenum? What is the rest known as?

Answer 3

Around 5m. 30cm. Ileum.

Question 4

What does the ileum do?

Answer 4

Absorbs digested food mainly. Some digestion takes place + also moves undigested food to large intestine (colon).

Question 5

What do all organs contain?

Answer 5

A range of tissues and tissue layers.

Question 6

What are the main tissue layers of the ileum? (inside to outside gut)

Answer 6

Mucosa, muscularis mucosa, submucosa, muscularis externa, + serosa.

Question 7

What is the mucosa made up of?

Answer 7

Simple columnar epithelial cells which absorb food molecules. (Amino acids, sugars, fatty acids absorbed through microvilli by active transport.) Also contains goblet cells for secretion of mucus to protect cells from self destruction. Crypts of Lieberkuhn (intestinal glands) with paneth cells. Further digestion takes place on epithelial cell surface membrane. Blood capillaries and lacteal help transport products of digestion.

Question 8

What increases the surface area of the mucosa?

Answer 8

Brush border of microvilli on epithelial cells. Also, villi themselves.

Question 9

What happens in the crypts of Lieberkuhn?

Answer 9

Cells at base are constantly dividing by mitosis to produce new epithelial cells. Migrate towards tip of villus where they’re sloughed off.

Question 10

What do paneth cells do?

Answer 10

Antimicrobial function to protect actively dividing stem cells at bottom of crypts. Also secrete enzymes (disaccharidase/peptidase)

Question 11

How does the muscularis mucosa perform its function?

Answer 11

Has small strands of muscle which extend from layer up through mucosa to each villus. When they contract, they help to produce the wafting movement of the villi.

Question 12

What does the submucosa contain?

Answer 12

Blood and lymphatic vessels and connective tissue.

Question 13

What does connective tissue do?

Answer 13

Provides support.

Question 14

What does the blood and lymph do?

Answer 14

Transport absorbed nutrients away from intestine (glucose/amino acids)

Question 15

Describe the muscularis externa.

Answer 15

Has an outer layer of longitudinal muscle which runs along the length of the alimentary canal and an inner layer of circular muscle which runs around the canal.

Question 16

What causes pendular movements and in which layer?

Answer 16

Contraction of longitudinal muscle in muscularis externa.

Question 17

What does contraction of circular muscle in the muscularis externa cause?

Answer 17

Local constrictions, helps to push food along gut in series of peristaltic waves.

Question 18

What is the point of pendular movements, local constrictions and peristalsis.

Answer 18

PM + LC help churn and mix food. P helps move food along the gut.

Question 19

How is the epithelium of the ileum adapted to maximise absorption?

Answer 19

Columnar epithelial cells of villus have microvilli which give brush border appearance, increasing surface area.
Digestive enzymes secreted into gut lumen or within cell surface membrane of CEC, microvilli increase enzyme no. which can make contact with food.
CEC have many mitochondria to produce ATP for active transport of absorbed food products.

Question 20

What are the main products of digestion which are absorbed in the ileum?

Answer 20

Glucose, amino acids, fatty acids + glycerol (Lipids). Also, vitamins and mineral ions.

Question 21

How are food products absorbed in ileum?:
Glucose + Amino Acids.
Lipid Soluble Products (Glycerol + FA’s).

Answer 21

Absorbed when touching CEC. Glucose + AA’s taken into CEC by active transport. Once inside cell, diffuse across cell + into capillary network as concs build up.
Diffuse into CEC lining villi. Inside cell, joined together to form triglyceride. Transported out of villi by lacteals in part of lymphatic system.

Question 22

What does mucus in goblet cells do?

Answer 22

Produces slimy protective layer which lubricates alimentary canal lining. This helps food move along gut + protects against digestive enzymes damaging epithelial lining.

Question 23

Where do most digestive activities in small intestine take place?

Answer 23

Duodenum

Question 24

Where do the digestive enzymes mainly come from? (3)

Answer 24

Liver, pancreas + small intestine wall.

Question 25

What does the liver do?

Answer 25

Produces bile which is stored in gall bladder + flows down bile duct into duodenum.

Question 26

What is the pH of the small intestine?

Answer 26

Alkaline.

Question 27

Where is pancreatic juice made + what does it do?

Answer 27

In pancreas by secretory cells. Released into pancreatic duct in response to acidic food in duodenum. Alkaline + neutralises stomach acid.

Question 28

What enzymes does pancreatic juice contain?

Answer 28

Trypsin, Chymotrypsin, Carboxypeptidase, Pancreatic Amylase, Lipase + Nuclease.

Question 29

What are released from secretory cells at tips of villi?

Answer 29

Enzymes which complete digestion. These are also present in cell surface membrane and cytoplasm of these cells.

Question 30

Give examples of enzymes from the small intestine.

Answer 30

Aminopeptidase, dipeptidase, nucleotidase, maltase, lactase + sucrase.

Question 31

What does the lacteal do?

Answer 31

Fatty acids and glycerol and fat droplets with bile salts pass into lymph.

Question 32

What is the glandular epithelium composed of?

Answer 32

Various cell types (stem cells, undifferentiated crypt cells, absorptive/columnar cells, goblet cells, paneth cells, enteroendocrine cells and M cells.

Question 33

How is the lamina of the leaf adapted for photosynthesis?

Answer 33

(Blade) Flat and thin. Provides large surface area for light absorption (more palisade cells) and gaseous exchange (more somata = more CO2).Surface area minimises water loss (e.g. cactus needle)

Question 34

How is the lamina attached to the stem/branch and what does this do?

Answer 34

Attached by leaf stalk/petiole which holds leaf in position so surface is exposed to max amount of light.

Question 35

Describe the stalk of the leaf.

Answer 35

From stalk, main vein (midrib) leads down leaf with side veins branching on either side. Connects leaf with rest of plant. Carry some raw materials for photosynthesis (water) + products away + give support (flat shape)

Question 36

What do palisade cells contain?

Answer 36

Many chloroplasts + large vacuoles to help incident light pass through layers.

Question 37

What is the most beneficial organisation of palisade cells?

Answer 37

Perpendicular to upper epidermis to max incident light on each cell + sugars moving to phloem sleeve.sieve tubes have to pass through fewer cells.

Question 38

What does the absorption of some products involve in the ileum?

Answer 38

Active transport and facilitated diffusion using carrier proteins.

Question 39

Describe the role of the capillaries within the villi.

Answer 39

Transport amino acids and monosaccharides out of villi. Combine to form venules of hepatic portal vein which transports digested products to liver. Capillary network maintains diffusion gradient from lumen to blood.

Question 40

How do guard cells work when turgid?

Answer 40

Cells expand and open pore to facilitate gas exchange. When less turgid, pore closes to reduce water loss.

Question 41

What occurs in the mucosa?

Answer 41

Absorption.

Question 42

How is the leaf adapted for minimising transpiration?

Answer 42

Waxy cuticle stops water leaving by evaporation. Stomata open + close by guard cells (at night) to reduce water loss.

Question 43

Why would spongy mesophyll cells not look like epidermal cells?

Answer 43

E cells wouldn’t have chloroplasts and would be tightly packed, unlike SM cells.

Question 44

Why might investigators take several biopsies when testing for coeliac disease?

Answer 44

Damage is patchy so taking more samples will improve the chance of finding symptoms.