digestive system Flashcards

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1
Q

digestive system

A

Digestive system is the system that breaks down the food taken into the body ready for absorption into the cells.

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2
Q

what do body cells need

A

simple sugars, amino acids, fatty acids, vitamins, minerals and water to function properly
Vitamins, minerals and water in the form of small molecules are able to pass through the differentially permeable membrane of the cell

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3
Q

what is digestion

A

the process by which carbohydrates, proteins and fats are broken down into products small enough to be absorbed into the blood and to the cells. It is the mechanical and chemical breakdown of food to small molecules that can be absorbed into the body.

simple sugars, fatty acids and amino acids are eaten as complex carbohydrates, proteins and fats. These molecules are large and must be broken down into smaller units before being absorbed into the cells.

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4
Q

what are the activities of digestion

A

Ingestion of food and water
Mechanical digestion of food
Chemical digestion of food
Movement of food along the alimentary canal
Absorption digested food and water into the blood and lymph
Elimination of material that is not absorbed

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5
Q

mouth cavity

A

mechanical digestion by teeth

chemical digestion of starch by salivary glands

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6
Q

pharynx

A

back of mouth cavity by moving up wards

throat that joins the mouth cavity to the oesophagus and larynx.

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7
Q

mechanical digestion

A

mechanical breakdown of food into smaller particles

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8
Q

chemical digestion

A

chemical breakdown of food into small molecules

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9
Q

saliva

A

fluid that is secreted into the mouth cavity by 3 pairs of salivary glands to begin digestion. It contains a mucous and digestive enzyme, salivary amylase, which begins the chemical digestion of starch, breaks down large starch molecules into smaller molecules.

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10
Q

how does ingestion occur in mouth

A

The action of jaw and teeth begins mechanical digestion, where food is broken into smaller products
Ingestion is the intake of food, liquids or drugs into the mouth.

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11
Q

what are the teeth made of?

A

4 incisors - chisel shaped teeth that are used for biting or cutting, like taking a bite out of an apple
2 canines - one on each side of the incisors. Conical teeth used for tearing. Same length as the other teeth, carnivorous animals have longer canines for tearing
4 premolars - 2 on each side of the jaw
6 molars - 3 on each side of the jaw.

same number occurs at top

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12
Q

oesophagus

A

tube 23-25cm that carries food from the throat (pharynx) to the stomach.

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13
Q

what is the oesophagus made of?

A

double layer of muscles, longitudinal an circular muscle

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14
Q

what is longitudinal muscle?

A

smooth muscle with fibres arranged lengthwise across an organ

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15
Q

smooth muscle

A

smooth muscle with fibres arranged in a circle around the organ (alimetnary canal in this case)

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16
Q

what is the stomach

what are the muscles of the stomach?

A

roughly j shaped enlarged section of the alimentary canal
mechanical digestion by churning action, waves of muscular contractions. chemical digestion by pepsin which begins protein digestion in infants, rennin coagulation milk protein.
contract in a variety of different ways to churn the food and mix it with the gastric juices, until food is converted into thick, soupy liquid called chyme.

longitudinal, oblique, circular.

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17
Q

what is the pyloric sphincter

A

band of circular muscle that regulates follow of material from the stomach to duodenum.

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18
Q

what is the pancreas

A

produces pancreatic juices containing enzymes for digesting proteins, lipids and nucleic acids.

19
Q

what is the small intestine

A

about 6m long after 2-8 hrs, contents of stomach moved to small intestine.
its lining secretes intestinal juice which contains many enzymes and the internal surface is lined with villi for absorption of digested food.

20
Q

what is the anus?

A

opening surrounding by the anal sphincter.

a muscle that can be voluntarily controlled.

21
Q

what is the salivary glands

A

3 pairs of glands produced saliva which dissolves food so it can be tasted. saliva contains mucous that lubricates mouth and food and holds food in the lump for swallowing. it also contains the enzyme salivary amylase, which begins the digestion of starch.

22
Q

what is the liver?

A

produces bile which is stored and concentrated in the gall bladder.
bile emulsifies lipids in the small intestine

23
Q

gall bladder

A

stores bile and releases it into the small intestine where the bile emulsifies lipids.

24
Q

duodenum?

A

first part of the small intestine

25
Q

what is the large intestine

A

has the transverse colon, ascending colon and descending colon
largest part of the intestine absorbs water, minerals, vitamins.

26
Q

caecum

A

first part of the large intestine

27
Q

appendix

A

no function in human

28
Q

rectum?

A

final part of the large intestine in which faces are formed

29
Q

what is peristalsis

A

Peristalsis are waves of muscular contraction that push food along the alimentary canal.

As the lump of food enters the pharynx and the oesophagus, the circular muscle behind it contracts to form a constriction.
By contraction of successive bands of circular muscle, the constriction moves in a wave along the oesophagus, pushing the food in front of it. This wave of constriction is called peristalsis

30
Q

how is food moved along the alimentary canal?

A

As the lump of food enters the pharynx and the oesophagus, the circular muscle behind it contracts to form a constriction.
By contraction of successive bands of circular muscle, the constriction moves in a wave along the oesophagus, pushing the food in front of it. This wave of constriction is called peristalsis

Movement of food along the alimentary canal is lubricated by the secretion of mucous from the inner lining of the oesophagus

31
Q

what is the mucosa

A

The stomach lining (mucosa) is specialised for secretion of gastric juices. This contains hcl, mucus and digestive enzymes.
Mucosa is a mucous membrane, the mucous membrane that forms the internal lining of the alimentary canal.

32
Q

what are gastric juices

A

Gastric juices are the digestive juices secreted by the gastric glands of the stomach.

33
Q

what are gastric glands

A

located in narrow tube like structures called gastric pits.

34
Q

why are nutrients not absorbed into the stomach

A

Nutrients are not absorbed into the blood through the stomach because the internal surface is covered by a thick layer of mucus. Some alcohol and other drugs like aspirin are absorbed in the stomach

35
Q

pyloric sphincter?

A

a ring of smooth muscle between the stomach and the duodenum.
At the lower end of the stomach, there is a thickening of the circular muscle resulting in a constriction. chyme is pushed through peristalsis

36
Q

digestion the s. intestine

A

Digestion continues in the small intestine under the influence of intestinal juices secreted by glands in the lining of small intestine, pancreatic juices are secreted by the pancreas and bile secreted by the liver and stored in the gall bladder, released into the small intestine.

37
Q

how is the villus suited to its function

A

Each villus is about 1 mm long and is covered by a single layer of cells
Inside the villus is a lymph capillary called a lacteal, which is surrounded by a network of blood capillaries
Absorption is further enhanced by continual movement of the villi brought about by the muscular movements of the intestinal walls.
This allows the villi to be in constant contact with different parts of the intestinal contents
These contents are constantly changing as new material is emptying into the small intestine from the stomach

38
Q

how does absorption take place in the villus

A

tion:
Some absorption occurs through simple diffusion as there is higher concentration of nutrient materials in the interior of the small intestine than in the cells lining the villi.
Absorption also takes place in active transport, which involves the cells of the villi using energy to take in nutrients against a concentration gradient that is, taking in molecules from low to high concentration.
From the walls of the villi, simple sugars, amino acids, water and water soluble substances are absorbed into the blood capillaries
Fatty acids and glycerol recombine in th cells of the villi to form fats
Substances that are absorbed into the blood capillaries, are carried by the hepatic portal vein to the liver
In the liver they may be removed for further processing or remain in the blood to be carried to other body cells.

39
Q

what is the large intestine

A

The large intestine is about 1.5 m long and is larger in diameter than small intestine
There are no villi
There are no digestive juices secreted
Lining secretes lots of mucus
Movement through the large intestine is slow 18-24 hrs
During this time, most of th e remaining water is absorbed, so contents are more solid.
Bacteria in l.i. breaks down remming organic compounds
Some bacteria produce vitamin which are aqfsored through walls into the blood. Mineral nutrients also absorbed
Faeces are the semi solid components left after water absorption and bacterial action. They contain water and undigested food material cellulose, bacteria and bile pigments and the remains of cells that have broken away from the internal lining of the alimentary canal
Defecation is not metabolic waste so not excretion it is elimination
Elimination is the removal of indigestible material, bacteria and bile pigments from the body.

The speed in which the material moves through the alimentary canal depends on its size and the contents of the meal
A large meal causes greater stretching for the stomach and material is pushed more quickly into the small intestine than when the stomach is less distended
High protein and high fat content in a meal slow the movement from the stomach to the small intestine
Alcohol and caffeine stimulate movements of the stomach

40
Q

what is constipation

A

A condition in which defecation is difficult , with faeces being hard and dry
Occurs if the movements of the large intestine are reduced and the contents remain there for a long period of time
As water is absorbed, the faeces become drier and harder
Defecation becomes difficult and painful
May be caused by the lack of roughage (cellulose or insoluble fibre which is. a component of plant food) in the diet.
Humans have no enzymes to digest cellulose, but is important as it stimulates movement in the alimentary canal
May also be caused by lack of exercise or emotional problems.

41
Q

what is diarrhoea

A

Diarrhoea is the frequent defecation of watery faeces.
Caused by the irritation of the small and large intestines, which increases peristalsis so that the contents of the intestines move through before threes adequate absorption of water
This irritation is caused by a bacterial or viral infection (bacteria that produce food poisoning). Cholera bacteria causes severe diarrhoea that death results from dehydration through loss of water from the intestines.

42
Q

what is bowel cancer?

A

Bowl or Colorectal cancer is an uncontrolled growth of cells in the wall of the large intestine
May be linked to diet, high alcohol consumption and smoking
A diet high in red meat and processed meat and low in fibre (fruits and vegetables) may increase the risk of developing this.
Risk factors involve being obese or overweight and physical inactivity.

43
Q

what is coeliac disease

A

People with this disease are unable to tolerate the protein gluten, which is found in wheat, rye and barley
If gluten is consumed by people with this condition, their immune system responds by damaging or destroying the villi in the small intestine
Without healthy villi, nutrients cannot be absorbed in the small intestine and the person becomes malnourished no matter how much food they eat.
Symptoms vary from person to person and involve muscle cramps, joint pain, tingling in the legs.
Some ppl may have no symptoms but are in full danger of being malnourished
It is inherited
No cure
Only follow a diet with no gluten