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biology > the Digestive System > Flashcards

the Digestive System Flashcards

1
Q

The digestive system

A

is a set of organs which transform food consumed into food that can be used in the body for energy, growth and repair.
* Rest is excreted as waste
* Process may take several hours

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2
Q

Digestion

A
  • A combination of different chemical reactions that act on the food we eat
  • Food is changed into the building blocks of nutrients to be absorbed and used by the body
  • Mechanical digestion
  • Chemical digestion
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3
Q

Stages of digestion

A

1-The mouth
ingestion, chewing and swallowing + starch digestion
2-The stomach
mixing and protein digestion
3-The small intestine
Carbohydrate and fat digestions; absorption
4-The large intestine
Waste and excretion

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4
Q

Enzymes

A
  • They are proteins
  • They act as catalysts making chemical changes happen while they themselves remain unchanged
  • They act on food, breaking it down into smaller pieces
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5
Q

The mouth

A

Mechanical breakdown
* The chewing action of the teeth
Chemical breakdown
* Saliva, secreted by the salivary glands contains salivary amylase
* Breaks down starch

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6
Q

Salivary glands

A

Three pairs:
* Parotid gland – below the ear
* Submandibular gland – below the tongue
* Sublingual gland – below the tongue

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7
Q

Saliva

A

Components
Water, mucus and salivary amylase
Functions
Lubricates the food with mucus making it easier to swallow Starts digestion – contains salivary amylase which breaks down starch into shorter polysaccharides Keeps the mouth and teeth clean

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8
Q

Tongue

A
  • A muscular organ
  • The muscles that attach the tongue are the extrinsic muscles of the tongue.
  • Inside the tongue, there are four pairs of intrinsic muscles that can
    alter the shape of the tongue for talking and swallowing
  • Held in place by attachments to the mandible and hyoid bone
  • Papillae cover the top – increase surface area + rough texture
  • Taste buds present in the papillae
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9
Q

Functions of the tongue

A
  • Taste
  • Tongue is covered with taste buds
  • Saltiness, sweetness, sourness, bitterness, savouriness
  • Does not have different regions specialized for different tastes
  • All regions of the tongue that detect taste respond to all five taste qualities
  • Chewing
  • Aids chewing by moving food around the mouth
  • Food is turned into a partially digested mass = bolus
  • Swallowing
  • The tongue pushes the bolus to the back of the mouth
  • During swallowing the trachea is blocked off by the epiglottis to stop food entering the lungs
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10
Q

5 tastes

A
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11
Q

Movement of food

A
  • Food is pushed to the back of the mouth towards the pharynx
  • It travels through the oesophagus to the stomach by peristalsis
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12
Q

Oesophagus

A
  • A muscular tube
  • From the pharynx to the stomach
  • Thin epithelium, no villi, a few glands secreting mucus
  • Circular and longitudinal muscles move the liquid food by peristalsis
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13
Q

The stomach

A
  • A J-shaped elastic organ
  • Expands and contacts depending on what is in it
  • Food enters from the oesophagus via the cardiac sphincter
  • A valve stops the backflow of the stomach’s contents
  • Food leaves through the pyloric sphincter into the duodenum
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14
Q

Four regions of the stomach

A
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15
Q

Stomach layers

A
  • 4 tunics, mucosa, submucosa, muscularis, & serosa or
    adventitia
  • Three layers of muscle to churn the food into a liquid called chyme
  • The mucosa of the stomach wall has no villi, but numerous gastric pits (104 cm-2 ) leading to gastric glands in the mucosa layer
  • Gastric rugae – folds in the mucosal and submucosal layers
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16
Q

Stomach functions

A

-Digests proteins through the action of enzymes
- Churns food with gastric juices
-Lubricates the food by producing mucus
-Absorbs alcoho-
- Kills bacteria by producing HCL
-Stores food – expandable bag

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17
Q

Gastric juices

A

HCL
*Neutralises bacteria and activates pepsin
Rennin
*Curdles milk protein (in infants)
Pepsin
*Changes proteins to polypeptides

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18
Q

The small intestine

A
  • 7 metres long
  • Divided into 3 sections
  • Duodenum
  • Jejunum
  • Ileum
  • Wall also contains 4 tunics
  • Epithelium in mucosa: simple columnar
  • Absorptive cells with microvilli
  • Goblet cells: secrete mucus
  • The mucosa is covered in villi which increase surface area for absorption
  • Circular folds - plicae circulares in the mucosa and submucosa
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19
Q

Functions of the small intestine

A

-Completion of chemical digestion of food
-Absorption of nutrients
-90% of the digestion and absorption of food occurs here
-Receives secretions from the pancreas and liver
-Protects the digestive system from infection

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20
Q

Digestion

A
  • Peristaltic movements mix food with intestinal and
    pancreatic juices and bile
  • Enzymes maltase, sucrase and lactase split disaccharides into monosaccharides
  • Enterokinase activates trypsin in pancreatic juice
  • Peptidases split polypeptides into amino acids
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21
Q

Absorption

A
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22
Q

The large intestine

A
  • Deals with waste
  • About 1.5m long
  • Sits draped around the small intestine
  • Consists of the caecum, appendix, colon, rectum, anal canal and anus.
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23
Q

Functions of larg intestine

A
  • Absorbs water and nutrients from digestive waste
  • Removes waste (faeces)
  • Faeces are undigested waste containing cellulose, fatty acids, mucus and dead cells
  • Bilirubin gives the faeces its colour
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24
Q

Protein digestion

A
  • Rennin (in gastric juice) converts the soluble milk protein casein into its insoluble calcium salt.
  • This keeps in the stomach longer so that pepsin can digest it.
  • Normally only produced by infant mammals.
  • Used commercially to make cheese.
  • Pepsin (in gastric juice) digests proteins to peptides, 6-12 amino acids long.
  • Pepsin is an endopeptidase, which means it hydrolyses peptide bonds in the middle of a polypeptide chain.
  • It has an optimum pH of about 2 and stops working at neutral pH
25
Q

Protein digestion

A
  • In the small intestine
    enzymes from the small
    intestine break down
    polypeptides into smaller
    chains
  • Trypsin
    – secreted as trypsinogen. Activated by enterokinase
  • Chymotrypsin
  • Aminopeptidases
26
Q

Carbohydrate digestion

A
  • Monosaccharides
  • E.g. glucose and fructose
  • Disaccharides
  • E.g. sucrose and lactose
  • Polysaccharides
  • E.g. starch and glycogen
  • All carbohydrates are broken down to monosaccharides for absorption
  • Become glucose to supply the body with energy
27
Q

Carbohydrate digestion

A

↓Salivary amylase starts the digestion of starch.
↓Very little digestion actually takes place
↓Amylase is quickly denatured in the stomach
↓Pancreatic amylase digests all the remaining starch in the duodenum.
↓Amylase digests starch molecules from the ends of the chains in twoglucose units, forming the disaccharide maltose. Glycogen is also digested here.
↓The carbohydrates that make up plant fibres (cellulose, hemicellulose, lignin, etc) cannot be digested, so pass through the digestive system as fibre.

28
Q

Fat digestion types

A

Saturated= Dairy products
Monounsaturated =Olive oil and avocado
Polyunsaturated =Sunflower oil and oily fish

29
Q

Fat digestion

A
  • Some polyunsaturated fats cannot be made by the body
  • Essential fats
  • Must be consumed in the diet
  • Must be broken down into fatty acids and glycerol to be used by the body
  • Emulsified by bile salts to form small oil droplets called micelles, which have a large surface area.
  • Pancreatic lipase enzymes digest triglycerides to fatty acids and glycerol in the duodenum.
  • Fatty acids and glycerol are lipid soluble and diffuse across the membrane (by lipid diffusion) into the epithelial cells of the villi in the ileum.
30
Q

Hormones Stimulate the production of pancreatic or intestinal juices and regulating acidity levels

A
  • Cholecystokinin CCK
  • secreted by the duodenum in response to chyme
  • Gastrin
  • Stimulates secretion of gastric acid (HCl) by the parietal cells of the stomach
  • Secretin
  • Stimulates release of pancreatic juice high in bicarbonate to buffer acidic chyme from stomach
  • Stimulates secretion of bile from liver
31
Q

Accessory organs

A

*Organs involved in the digestive process, but the food
never passes through them
* Tongue, teeth, salivary glands, liver, pancreas and gall
bladder
*Help in the digestive process

32
Q

Teeth

A
  • Adult humans should have 32 teeth, 16 in the upper jaw and 16 in the lower jaw. There are two incisors, a canine, two premolars and three molars on each side of each jaw.
33
Q

Tooth structure

A
  • Consists of enamel, dentin, cementum and pulp tissue.
  • The portion of a tooth exposed to the oral cavity is known as the dental crown
  • The portion below the dental crown is known as the tooth root.
  • The dental pulp cavity exists in the centre of the tooth
34
Q

Teeth

A

-Incisors
flat and sharp-edged for cutting off food.
-Canines
short and pointed and are not so prominent as in the carnivores. They are used to cut off food.
-Premolars and molars
flattened surfaces with sharp ridge and cusps. They are used for crushing and grinding food

35
Q

Baby teeth

A
  • In humans, there are 20 deciduous teeth and 32 permanent teeth
36
Q

Liver

A
  • The largest gland in the body
  • Located in the upper right-hand portion of the abdominal cavity, beneath the diaphragm, and on top of the stomach, right kidney, and intestines
  • Double blood supply
  • Oxygenated blood flows in from the hepatic artery
  • Nutrient-rich blood flows in from the hepatic portal vein
  • Holds 13% of the body’s blood supply
  • Consists of two main lobes
37
Q

Liver functions

A

1-Removes
* Toxins from drugs, alcohol and harmful substances
* Nitrogen from amino acids
2-Stores
* Vitamins A, B12, D, E and K
* Glycogen, iron and fats
3-Produces
* Heat
* Vitamin A and Vitamin D
* Heparin
* Plasma proteins: albumin, globulin, prothrombin, fibrinogen
* Bile
* Uric acid and urea
4-Converts
* Stored fats into other fat products e.g. cholesterol
* Glycogen to glucose
* Glucose to glycogen
* Metabolises protein

38
Q

Bile

A
  • A thick liquid produced in the liver from the breakdown of red blood cells
  • Contains salts, pigments, acids and water
  • Emulsifies fats, stimulates peristalsis and creates alkaline conditions in the small intestine
39
Q

The gall bladder

A
  • A pear shaped sac attached to
    the cystic and bile ducts to the
    posterior of the liver
  • Excess bile is stored in the gall
    bladder until needed
40
Q

Gall bladder functions

A
41
Q

The pancreas

A
  • A gland situated posterior to the stomach, between the duodenum and spleen
  • Delivers pancreatic juices to the duodenum through the pancreatic duct
  • Cells of the pancreas are divided into:
  • Islets of Langerhans – produce insulin and glucagon
  • Alveoli - produce enzymes
42
Q

The pancreas Functions

A

Produces enzymes to digest food Produces the hormone insulin and glucagon Pancreatic juice contains enzymes:
* Lipase – fat digestion
* Amylase – starch digestion
* Trypsin – protein digestion

43
Q

Insulin

A
  • Hormone secreted by beta cells in the islets of Langerhans
  • Regulates blood sugar level
  • Blood sugar level rises after eating
  • Insulin helps absorb glucose and changes excess glucose to glycogen
  • A lack of insulin causes diabetes mellitus
  • Type 1 diabetes – caused by autoimmune damage
  • Type 2 diabetes – insulin resistance
44
Q

Anorexia

A
  • Loss of appetite
  • A psychological condition
  • Sufferers have a fear of gaining weight
  • Sometimes fatal
45
Q

Appendicitis

A
  • Acute inflammation of the appendix
  • Usually treated by removal of the organ
  • appendectomy
46
Q

Gall stones

A
  • Stones formed from residues of bile pigments, cholesterol and calcium salts found in the gall bladder
47
Q

Heartburn

A
  • Burning sensation in the oesophagus or throat
  • Caused by backflow and regurgitation of acid stomach contents
  • Gastroesophageal reflux disease
48
Q

Hiatal hernia

A
  • Stomach bulges up through the hiatal opening
  • Hiatus = opening in the diaphrapm
  • Two types of hiatal hernia
  • Sliding
  • The stomach and the section of the oesophagus that joins the stomach slide up into the chest through the hiatus
  • Most common type
  • Paraoesophageal/rolling
  • Part of the stomach squeezes through the hiatus landing it next to the oesophagus
  • Stomach can become strangled or have its blood supply shut off
49
Q

Jaundice

A
  • Caused by a build-up of bilirubin, a bile pigment in the blood
  • An inflamed liver or obstructed bile duct can lead to jaundice
  • Symptoms include a yellow tinge to the skin and whites of the eyes, dark urine and itchiness
50
Q

Neonatal jaundice

A
  • Yellow discoloration of a newborn baby’s skin
    and eyes
  • A common condition, particularly in babies born
    before 38 weeks’ gestation
51
Q

Irritable bowel syndrome

A
  • No exact cause is known
  • Stress, low fibre and high fat diets are said to contribute
  • Symptoms include stomach and bowel pain and alternate bouts of diarrhoea and constipation
52
Q

Inflammatory bowel disease (IBD)

A
  • Used to describe disorders that involve chronic inflammation of your digestive tract
  • Ulcerative colitis - condition causes long-lasting inflammation and sores (ulcers) in the innermost lining of your large intestine (colon) and rectum
  • Crohn’s disease - characterized by inflammation of the lining of your digestive tract, which often spreads deep into affected tissues
53
Q

Coeliac’s disease

A
  • Caused by an adverse reaction to gluten found in wheat, barley and rye
  • An autoimmune condition which damages the surface of the small intestines
  • Eating foods containing gluten can trigger a range of gut-related symptoms, such as diarrhoea, abdominal pain, bloating and flatulence, indigestion and constipation
  • Other symptoms include: fatigue, unexpected weight loss, an itchy rash
54
Q

Importance of nutrients

A
  • A balanced diet is one that gives your body the nutrients it needs to function correctly
  • Proteins are used to build and repair tissues and help fight infection
  • Carbohydrates are the body’s main source of energy
  • Fats supply energy, and they help the body absorb certain vitamins
55
Q

Essential nutrients

A
  • Essential amino acids
  • The body requires 20 different amino acids.
  • 9 essential amino acids cannot be manufactured by the body and must be obtained through the diet
  • Essential fatty acids
  • An unsaturated fatty acid that is essential to human health, but cannot be manufactured in the body. Must be obtained through the diet
56
Q

Food and metabolism

A
  • Metabolism refers to all the chemical processes going on continuously inside your body that allow life and normal functioning
  • Building and repairing the body requires energy that
    ultimately comes from the food we eat
  • The amount of energy, measured in kilojoules (kJ), that your body burns at any given time is affected by your metabolism
57
Q

Metabolic processes

A
58
Q

Metabolic rate

A

biology (15 decks)

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