Digestive System Flashcards
1
Q
What is the importance of nutrients in digestion?
A
The digestive system** extracts nutrients** from food and absorbs them into the body for use by the cells.
2
Q
What are the processes of the digestive system?
A
- Ingestion of food and water
- mechanical digestion of food
- chemical digestion of food
- movement of food along the alimentary canal
- absorption of digested food and water
- elimination of waste material that is not absorbed
3
Q
What are nutrients?
A
Any substance that provides energy, is essential for growth, or assists in the functioning of the body.
4
Q
What are the main types of nutrients?
A
Water, minerals, vitamins, carbohydrates, proteins, lipids.
5
Q
What is the main energy source for the cell?
A
Carbohydrates
6
Q
What are the types of carbohydrates?
A
- Monosaccharides (e.g., glucose, fructose, galactose)
- disaccharides (e.g., sucrose, maltose, lactose)
- polysaccharides (e.g., glycogen, cellulose, starch)
7
Q
What are lipids broken down into?
A
Fatty acids and glycerol for cellular respiration
8
Q
What is the structure of lipid molecules?
A
Made of one glycerol molecule and 1-3 fatty acid molecules
- triglycerides = most common
9
Q
What is the function of proteins?
A
Control cellular processes and build and repair cells
10
Q
How many types of amino acids are there?
A
There are 20 different types of amino acids, of which 9 must be obtained from food.
11
Q
What is a dipeptide?
A
Two amino acids bonded by a peptide bond.
12
Q
What is a polypeptide?
A
More than 10 amino acids.
13
Q
What is a protein?
A
100 or more amino acids.
14
Q
What are organic compounds?
A
Compounds that contain a carbon chain, usually bonded to hydrogen
- carbohydrates
- proteins
- lipids
- RNA
- DNA
- vitamins
15
Q
What are inorganic compounds?
A
Compounds that are not based on a carbon chain, usually do not contain carbon
- water
- minerals
16
Q
What are the functions of nutrients?
A
carbs: provide energy for cells
proteins: build and repair cells
lipids: regulate body processes
17
Q
What are carbohydrates made out of?
A
- Hydrogen
- carbon
- oxygen
twice as many hydrogen atoms as oxygen
18
Q
What happens to excess protein in the body?
A
Converted to carbohydrates and used as an energy source.
19
Q
What can hormones be made of?
A
can be proteins (e.g., insulin) or lipids (e.g., estrogen).
20
Q
What is protein made up of?
A
- carbon
- hydrogen
- oxygen
- nitrogen
- often sulfur and phosphorus
21
Q
What are lipids made from?
A
- carbon
- hydrogen
- oxygen
less oxygen than carbohydrates
22
Q
What is the role of nucleic acids?
A
Essential in forming DNA and RNA that stores genetic information.
23
Q
What is the composition of nucleic acids?
A
- carbon
- hydrogen
- oxygen
- nitrogen
- phosphorus
- nucleotides:containing a nitrogen base, a sugar, and a phosphate
24
Q
What are vitamins?
A
Small organic compounds that don’t provide energy but are essential for cells to gain energy from carbohydrates, lipids, and proteins.
act as **co-enzymes **for chemical reactions of metabolism
25
What are minerals?
May be part of **enzymes**, **cofactors**, or **substances involved in metabolism**, with 20 mineral elements essential for human body functioning.
26
What are the functions of water in the body?
- Regulation of body temperature through perspiration, excretion of wastes
- serving as a solvent for other substances.
27
How much water makes up the body?
Water makes up about 70% of the total weight of the body.
28
What needs to happen to nutrients for them to be absorbed?
Vitamins, minerals, and water must be ***small enough to pass through the semi-permeable cell membrane***
carbohydrates, proteins, and lipids need to be ***broken down***.
29
What is digestion?
The process of breaking down food particles small enough to be absorbed into the bloodstream.
30
What is mechanical digestion?
The physical breakdown of food to increase the surface area.
31
What is the aim of mechanical digestion?
To increase surface area for more successful chemical digestion.
32
What is chemical digestion?
The breakdown of complex molecules from food to smaller, simpler molecules by chemicals, **referring only to enzyme action**.
33
What makes up the alimentary canal?
- mouth
- oesophagus
- stomach
- small intestine
- large intestine
- rectum, and anus.
34
What are the accessory organs of the digestive system?
Pancreas, liver, gallbladder.
35
What is mastication?
The process of chewing food, done by teeth.
36
What are the types of teeth?
- **Incisors** -chisel-shaped, ***biting/cutting*** teeth (4)
- **Canines** - sharp conical, ***tearing*** teeth (2)
- **Pre-molars** - flat crowns, ***grinding*** teeth (4)
- **Molars** - flat broad crowns ***crushing*** (or grinding) teeth (6)
37
What happens after food is chewed in the mouth?
It is formed into a bolus by the tongue and pushed towards the pharynx for swallowing.
38
What is the structure of the oesophagus?
A tube about 23-25cm long with a double layer of muscle.
39
What happens to food in the oesophagus?
Food moves through the pharynx to the stomach, lubricated by mucus and moved by peristalsis.
40
What is the function of the epiglottis?
Closes off the trachea, preventing food from entering the lungs.
41
What is peristalsis?
The **wave-like muscle contractions** that move food through a tube such as the oesophagus.
42
What happens in the stomach during mechanical digestion?
Waves of muscular contraction churn food to produce chyme.
43
What are the layers of muscle in the stomach?
Circular layer, longitudinal layer, and additional oblique layer.
44
What is the chemical digestion in the stomach?
Enzymes in gastric juice secreted by gastric glands.
45
What are the contents of gastric juice?
- HCl (destroys bacteria)
- mucus (protects stomach tissue)
- pepsinogen (activated to pepsin)
46
What is the function of gastric glands?
Located in gastric pits, they secrete gastric juice.
47
What is the pyloric sphincter?
A thickening of circular muscle at the bottom of the stomach that controls the flow of material into the duodenum.
48
How long does food usually stay in the stomach?
Pushed through after 2-8 hours.
49
What can be absorbed in the stomach?
Alcohol, glucose, and drugs (e.g., aspirin).
50
What is the structure of the small intestine?
6m long and consists of
three sections: Duodenum, Jejunum, Ileum.
51
What is segmentation in the small intestine?
Circular muscle contraction that breaks up the bolus further and brings it into contact with the lining for absorption.
52
What is bile?
Produced in the **liver**
stored in the **gallbladder**
enters the intestine through the **common bile duct**
- doesn’t contain enzymes so is a mechanical digestion*
53
What is the role of bile?
- maintains intestinal pH by neutralizing stomach acids
- physically breaks down large fat droplets
54
What are the pancreatic enzymes?
- **Amylase**: starch -> maltose
- **Trypsin**: proteins -> polypeptides
- **Lipase**: lipids -> fatty acids and glycerol
- **Ribonuclease and Deoxyribonuclease**: digests RNA and DNA
55
What are intestinal enzymes?
**Maltase**: maltose -> glucose
**Sucrase**: sucrose -> glucose
**Lactase**: lactose -> fructose
**Peptidase**: dipeptides -> amino acids
**Lipase:** : lipids -> fatty acids and glycerol
56
What makes absorption more efficient in the small intestine?
Surface area:
- long length (6m)
- highly folded inner lining walls (mucosa)
- villi
- microvilli
- extensive capillary network
57
What is a villus?
1mm long and covered by a single layer of cells with a single lymph capillary (lacteal) surrounded by blood capillaries
*muscular contractions in the small intestine that keep the contents moving along to maintain the concentration gradient*
58
How are nutrients transported in the small intestine?
Monosaccharides and amino acids via active transport, water and minerals via osmosis, fatty acids and glycerol via simple diffusion.
59
What is the pathway of nutrient transport in the small intestine?
**Monosaccharides**
***Active transport** into the blood capillaries*
**Amino acids**
***Active transport** into the blood capillaries*
**Water, minerals and water-soluble vitamins**
***Osmosis** into blood capillaries*
**Fatty acids and glycerol, and lipid-soluble vitamins**
***Simple diffusion** into the villi where they recombine and then enter the lacteal*
60
What is the structure of the large intestine?
- 1.5m long
- made up of caecum, appendix, colon, rectum, and anus *(external opening with anal sphincter)*
61
What happens in the large intestine?
Contents are pushed into the rectum by peristalsis
absorbs remaining water *(making contents solid)*, minerals and vitamins *(that are produced from bacteria)*
62
What is defaecation?
Triggered as the walls stretch, resulting in the **passing out of faeces**
referred to as **elimination** (NOT EXCRETION)
***excretion** = removal of **metabolic** waste (waste produced from chemical reactions)
**elimination** = removal of indigestible material, bacteria and bile pigments from the body*
63
What are the contents of faeces?
- water
- undigested food (mainly cellulose)
- bacteria
- bile pigments
- remains of cells from the canal lining.
64
What is ingestion?
The intake of food, liquids, or drugs into the mouth.
65
What is the function of the oral cavity/mouth?
Ingestion of food.
66
What is the function of the oesophagus?
Connects pharynx to the stomach.
67
What is the function of the duodenum?
Continues chemical digestion (of proteins) in the small intestine.
68
What is the function of the jejunum?
Absorption of carbohydrates and proteins in the small intestine.
69
What is the function of the ileum?
Remaining products of digestion are absorbed.
70
What is the role of segmentation?
Breaks up the bolus further and mixes contents with juices and bile.
71
How long does food stay in the large intestine?
18-24 hours to pass through.
72
What are the functions of the stomach?
- Mechanical digestion through churning to create chyme
- chemical digestion of pepsin to digest proteins
- creating an acidic environment through HCl
73
What is the function of the large intestine?
- Absorbs water and vitamins
- stores faeces
- facilitates defaecation
74
What is the pathway of bile?
Liver -> gallbladder -> common bile duct -> small intestine.
75
What are other carbohydrate enzymes?
sucrase breaks down sucrose into glucose
lactase breaks down lactose into fructose
maltase breaks down maltose into glucose
76
What are the features of villi (MR SLIM)?
- **M**icrovilli increase surface area
- **R**ich blood supply rapidly
-** T**ransports absorbed products
- **S**ingle layer epithelium minimizes diffusion distance
- **L**acteals absorb lipids
- **I**ntestinal glands release digestive juices.
- **M**embrane proteins – Facilitates transport of digested materials into epithelial cells
77
What are the type of cells on the lining of the villus?
**epithelial** - absorptive cell
**goblet** - secretory cell
78
Rectum
facilitates defaecation through peristalsis
79
Colon
*longest part of the small intestine*
**sections**
-ascending
- transverse
- descending
80
Caecum
pouch about 6cm long that **joins small intestine to large intestine**
81
Appendix
small tube attached to caecum
