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CCEA AS Biology Unit 1 > U1T7 - Tissues & Organs > Flashcards

U1T7 - Tissues & Organs Flashcards

1
Q

What is the point of peristaltic contractions in the stomach?

A

Keep the chyme moving towards the duodenum.

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2
Q

What does the pyloric sphincter do?

A

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

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3
Q

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

A

Around 5m. 30cm. Ileum.

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4
Q

What does the ileum do?

A

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

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5
Q

What do all organs contain?

A

A range of tissues and tissue layers.

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6
Q

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

A

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

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7
Q

What is the mucosa made up of?

A

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.

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8
Q

What increases the surface area of the mucosa?

A

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

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9
Q

What happens in the crypts of Lieberkuhn?

A

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

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10
Q

What do paneth cells do?

A

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

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11
Q

How does the muscularis mucosa perform its function?

A

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.

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12
Q

What does the submucosa contain?

A

Blood and lymphatic vessels and connective tissue.

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13
Q

What does connective tissue do?

A

Provides support.

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14
Q

What does the blood and lymph do?

A

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

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15
Q

Describe the muscularis externa.

A

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.

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16
Q

What causes pendular movements and in which layer?

A

Contraction of longitudinal muscle in muscularis externa.

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17
Q

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

A

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

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18
Q

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

A

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

19
Q

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

A

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.

20
Q

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

A

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

21
Q

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

A

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.

22
Q

What does mucus in goblet cells do?

A

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

23
Q

Where do most digestive activities in small intestine take place?

A

Duodenum

24
Q

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

A

Liver, pancreas + small intestine wall.

25
Q

What does the liver do?

A

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

26
Q

What is the pH of the small intestine?

A

Alkaline.

27
Q

Where is pancreatic juice made + what does it do?

A

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

28
Q

What enzymes does pancreatic juice contain?

A

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

29
Q

What are released from secretory cells at tips of villi?

A

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

30
Q

Give examples of enzymes from the small intestine.

A

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

31
Q

What does the lacteal do?

A

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

32
Q

What is the glandular epithelium composed of?

A

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

33
Q

How is the lamina of the leaf adapted for photosynthesis?

A

(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)

34
Q

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

A

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

35
Q

Describe the stalk of the leaf.

A

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)

36
Q

What do palisade cells contain?

A

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

37
Q

What is the most beneficial organisation of palisade cells?

A

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

38
Q

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

A

Active transport and facilitated diffusion using carrier proteins.

39
Q

Describe the role of the capillaries within the villi.

A

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.

40
Q

How do guard cells work when turgid?

A

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

41
Q

What occurs in the mucosa?

A

Absorption.

42
Q

How is the leaf adapted for minimising transpiration?

A

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

43
Q

Why would spongy mesophyll cells not look like epidermal cells?

A

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

44
Q

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

A

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

CCEA AS Biology Unit 1 (14 decks)

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