Digestive system Flashcards
Ingestion-
Ingestion- the taking of food, drugs, liquids, or other substances into the body by mouth.
Digestion
Digestion – the breakdown of large insoluble molecules, into smaller soluble molecules which can be absorbed
Absorption
Absorption – The passage of the soluble products of digestion from the gastro-intestinal tract into the blood, lymph vessels, cells and tissues.
Assimilation
Assimilation - Incorporation of digested materials from food into the tissues. e.g. anabolic reactions
What is the enzyme for Starch
amylase
What is the enzyme for Maltose
maltase
What is the enzyme for Proteins
Pepsin ,Trypsin, chymotrypsin
What is the enzyme for Peptides
Carboxypeptidase
What is the enzyme for Lipids
lipase
What doe starch get broken down into
Maltose
What doe maltose get broken down into
glucose
What do proteins get broken down into
peptides
What do peptides get broken down into
amino acids
What do lipids get broken down into
fatty acids and glcerol
Where is amylase
Mouth
What are the general structures of GI tract
see paper
Label GI tract
See picutre
Identify the different parts see pcitire (3)
See notes
What is the mucosa
A mucous membrane (makes mucus) 3 parts: A) Epithelium – varies in different parts of gut - it often indents to form glands Epithelium in upper GI tract is mainly non-keratinised stratified squamous epithelium
) Areolar loose connective (lamina propria)
- Contains blood vessels, lymph (vascular support for the epithelium) - Often contains mucosal glands - Lymphoid follicles, and plasma cells are also often found here. - Function is support, absorption, immunity
C) Thin double layer of smooth muscle (muscularis mucosa) – this moves the mucosa
Submucosa
Made of areolar (loose) connective tissue
With many larger bv’s and lymph vessels
And the enteric nervous system (ENS), a network of neurones (AKA Meissner’s plexus)
Can contain mucous secreting glands.
- Muscle layer (muscularis)
In upper GI tract is skeletal muscle
Eg in mouth, pharynx, upper oesophagus
In lower GI tract is smooth muscle – not under voluntary control
There are usually two layers (apart from stomach); the inner layer is circular, and the outer layer is longitudinal.
These layers of smooth muscle are used for peristalsis (rhythmic waves of contraction), to move food down through the gut.
- Serosa v
Adventia layer (or serosa)
outermost layer of loose connective tissue - covered by the visceral peritoneum. Contains blood vessels, lymphatics and nerves.
Label inner lining of oesphagus
1- epithelia
2 - lamina propria
3, musculaire mucosa
4, submucosa
What is picture H
see hand out
Describe the stomach ? what does it do ?
A muscular bag
Produces enzymes to break down food
Contains acid to kill microorganisms and help enzymes work
Acid does not digest your food for you!
special chemicals called enzymes break down the food even more. pepsin, an enzyme produced by stomach mucosa which helps to digest protein molecules to peptides.
Small intestine function
More enzymes added to finish digestion
Absorption of digested food takes place here
In the small intestine, the broken down food gets into the blood so the body can use it.
Here food is mixed with digestive juices from the liver and pancreas.
Label diagram of general digestive organs
See sheet 1 mouth 2 pharynx 3 tongue 4 oesophagus 5 pancreas 6 stomach 7 liver 8 gallbladder 9 duodenum 10 ascending colon 11 ileum 12 anus 13 rectum 14 sigmoid colon 15 jejunum 16 descending colon and transverse colon (bit touching stomach )
What happens in Small intestine
Duodenum
Ileum
Breaks down carbohydrates
Protein
Fat
In the small intestine, the broken down food gets into the blood so the body can use it.
Here food is mixed with digestive juices from the liver and pancreas.
Large intestine
The large intestine is about 1.5 metres long.
In the large intestine, the body absorbs a lot of water back from the digested food.
Water goes from food into the blood stream
Rectum
When your food has been through the Large Intestine only waste products remain (Rectum).
Semi-solid faeces are formed after 12-36 hours in the large intestine. Faeces are stored in the rectum until they are egested
anus
faeces exit through your anus. This is called egestion.
Anus, a ring of muscle which prevents faeces from leaving the body until ready
How do you determine the energy value of food
4.2 is the value of the specific heat capacity of water, in joules per gram per degree Celsius – the number of joules taken to raise the temperature of water by 1ºC.
1 cm3 of water has a mass of 1 g.
If the number is more than 1000 J/g, express it as kilojoules (kJ):
1 kilojoule = 1000 joules
Energy lreeased from food = mass water x temperature rise/ mass of food sample
The sympathetic and parasympathetic nervous system in regards to digestion
The SNS is responsible for the Flight or Fight response of the body.
When we get scared, the SNS increases our heart rate and provides energy to our muscles in preparation for action.
In order to provide more energy to the heart, lungs and muscle, it inhibits (slows or stops) digestion by directing blood flow away from the digestive tract.
The PNS is responsible for stimulating digestion by increasing blood flow to the digestive tract. The PNS stimulates salivary gland secretion and increases peristalsis. This increases the digestion of food and absorption of nutrients.
How does nervous control work in digestion
When food touches an organ it puts pressure on special receptors that are in the lining of the organ.
The receptors send nerve impulses (messages) to the brain.
The brain then sends a message back to the organ (e.g. the stomach ) and tells it what to do (like telling the gastric glands to release gastric juice or telling the muscles of the stomach to start contracting).
What nerves are involved in digestion
Two types of nerves help to control the action of the digestive system.
Extrinsic (outside) nerves come to the digestive organs from the unconscious part of the brain or from the spinal cord .
Acetylcholine causes the muscle of the digestive organs to squeeze with more force and increase the “push” of food and juice through the digestive tract. Acetylcholine also causes the stomach and pancreas to produce more digestive juice.
Adrenaline relaxes the muscle of the stomach and intestine and decreases the flow of blood to these organs.
Intrinsic (inside) nerves, which make up a very dense network embedded in the walls of the oesophagus, stomach, small intestine, and colon.
The intrinsic nerves are triggered to act when the walls of the hollow organs are stretched by food.
They release many different substances that speed up or delay the movement of food and the production of juices by the digestive organs
What is number 9 on digestive organs
duodenum
What is number 10 on digestive organs
ascending colon
What is number 11 on digestive organs
ileum
What is number 12 on digestive organs
anus
What is number 13 on digestive organs
rectum
What is number 14 on digestive organs
sigmoid colon
What is number 15 on digestive organs
jejunum
What is number 16 on digestive organs
transcending colon ( next to stomach) and descending colon
What is number 1 on digestive organs
mouth
What is number 2 on digestive organs
pharynx
What is number 3 on digestive organs
tongue
What is number 4 on digestive organs
oesphagus
What is number 5 on digestive organs
pancreas
What is number 6 on digestive organs
stomach
How to calculate energy change of food
Burn food samples under a boiling tube containing a measured amount of water. Measure the temperature increase in the water. Calculate the amount of energy needed to cause that temperature increase. This gives an estimate of the amount of energy stored in the food.
What Ph do pepsin work between
1-4
What Ph do salivary amylase work between
4-8.5
What Ph do alkaline phosphate work between
7-10.5?
Define perusalis
Throughout its journey, the food is squeezed down the digestive system by muscular walls in a process called peristalsis.
What is picture A and describe it
Oesophagus
Regional variations - oesophagus in cross section sows a stellate type lumen resulting from folding of the muscose (M) typical of the relaxed state. the muscular mucosal (MM) of smooth muscle is noted; surrounding the submucosa ((sm) the muscular external of smooth muscle show the inner circular (IC0 AND OUT LONGITUDINAL LAYERS. WITH TEH INTOrodction of food bolus, a peristaltic wave of contraction of the muscle is ignited, lasting 6-7 seconds. the upper and lower ends of the oesophagus have sphincters ( the lower one is not histologically distant ) which relax in association with the transport of a bolus along he oesophagus . the stratified squamous epithelia epitheliumexts against what and tear.
What is picture B
oesophagus
What is picture c
oesophagus wall
Describe gross structure of the stomach
Food starts to be digested and absorbed in the stomach, although absorption is mostly limited to water, alcohol and some drugs.
The stomach is an expandable, muscular bag, and it keeps swallowed food inside it by contracting the muscular pyloric sphincter.
Food can stay in the stomach for 2 hours or more. Food is broken down chemically, by gastric juice, and mechanically, by contraction of the three layers of smooth muscle in the muscular externa layer.
The broken up food at the end of this process is called
Label D 1
Oesophagi
Label D 2
Fundus
Label D 3
Rugae (folds of the stomach)
Label D 4
Pyloric region
Label D 5
pyloric sphincter
Label D 6
duodenum
Label D 7
Body of stomach
Label D 8
Cardiac region
Identify e
stomach histology
Describe mucosa of the stomach
The mucosa of the stomach consists of the epithelium and the lamina propria (composed of loose connective tissue), with a thin layer of smooth muscle called the muscularis mucosae separating it from the submucosa beneath.
Submucosa of the stomach
The submucosa lies under the mucosa and consists of fibrous connective tissue, separating the mucosa from the next layer.
Muscularis externa
of the stomach
The inner oblique layer: This layer is responsible for creating the motion that churns and physically breaks down the food. It is the only layer of the three which is not seen in other parts of the digestive systemThe Middle circular layer: pyloric sphincter, which controls the movement of chyme into the duodenum. The outer longitudinal layer
Serosa
of stomach
A smooth membrane consisting of a thin layer of cells which secrete serous fluid, and an underlying thin epithelial layer. The Latin anatomical name is tunica serosa. where they secrete a lubricating fluid which reduces friction from muscle movement.
adventitia of stomach
Adventitia, a connective tissue layer which binds together structures rather than reducing friction between them.
Oxyntic / parietal cells in stomach what do they do
Oxyntic / parietal cells – produce hydrochloric acid
Chief cells in stomach what do they do
produce pepsinogen
Gastric pits (simple columnar epithelium) – in stomach what do they do
Gastric pits (simple columnar epithelium) – gastric glands which release gastric juice
Goblet cells – in stomach what do they do
Goblet cells – produce mucous forming the mucous layer
Mucous layer in stomach what do they do
Mucous layer – protects stomach and prevents autodigestion
Musculature of stomach (3 layers of muscle long/circ/oblique) – in stomach what do they do
Musculature of stomach (3 layers of muscle long/circ/oblique) – helps mechanical digestion by churning of the stomach
Rugae (large folds) – in stomach what do they do
Rugae (large folds) – to accommodate a large volume of food after eating
Serosa in stomach what do they do
Serosa decreases friction and protects organs
In stomach -decreases friction and protects organs
Serosa
In stomach -to accommodate a large volume of food after eating
Rugae (large folds) –
In stomach -) – helps mechanical digestion by churning of the stomach
Musculature of stomach (3 layers of muscle long/circ/oblique
In stomach -protects stomach and prevents autodigestion
Mucous layer –
In stomach -produce mucous forming the mucous layer
Goblet cells –
In stomach -gastric glands which release gastric juice
Gastric pits (simple columnar epithelium) –
In stomach -produce hydrochloric acid
Oxyntic / parietal cells –
In stomach -produce pepsinogen
Chief cells –
What is secreted by gastric mucosal glands
Gastric juice is secreted by gastric mucosal glands, and contains hydrochloric acid, mucus, and proteolytic enzymes pepsin (which breaks down proteins), and lipase (which breaks down fats).
What does gastric juice contain
Gastric juice is secreted by gastric mucosal glands, and contains hydrochloric acid, mucus, and proteolytic enzymes pepsin (which breaks down proteins), and lipase (which breaks down fats).
What happens to the rugae when stomach is empty
When the stomach is empty, and not distended, the lining is thrown up into folds called rugae. After eating, these folds flatten, and the stomach is able to distend greatly.
What happens to the rugae when stomach is full
When the stomach is empty, and not distended, the lining is thrown up into folds called rugae. After eating, these folds flatten, and the stomach is able to distend greatly.
Cardiac region of stomach
It contains mainly mucous secreting glands –prevent auto digestion and protection to stomach
IDENTIFY PICTURE x and label
cardiac region of stomach
Fundus region
It contains numerous gastric pits – release gastric juice
Parietal/ oxyntic cells – produce HCl
Chief cells – produce pepsinogen
Surface mucous cells – mucous layer prevents autodigestion
Identify picture G and label
funds region
How is pepsinogen coverted to pepsin
On contact with HCl
H+ ions interacts with side chains in the pepsinogen molecule. This changes the tertiary structure of pepsinogen,
Exposing the active site.
Also coming into contact with other pepsin molecules
Hydrolyses small sections from pepsinogen
Pyloric region of stomach
Pyloric glands (deeper pits, shorter and more branched glands)
Fewer parietal cells more mucosa secreting cells
G cells – secrete hormone gastrin (stimulates secretion of pepsin and acid)
ends at the pyloric sphincter. This sphincter relaxes when the formation of chyme is completed, and the chyme is squirted into the duodenum.
LABEL K and identify
Pyloric region
Duodenum and ileum -huge surface area for absorption
The main functions of the small intestine are digestion, absorption of food and production of gastrointestinal hormones.
The small intestine is 4-6 metres long in humans.
To aid in digestion and absorption:
the small intestine secretes enzymes and has mucous producing glands. The pancreas and liver also deliver their exocrine secretions into the duodenum.
The mucosa is highly folded.
large circular folds called plicae circulares most numerous in the upper part of the small intestine
smaller folds called villi, which are finger like mucosal projections, about 1mm long.
the lining columnar epithelial cells have fine projections on their apical surfaces called microvilli
Duodenum
First section of the small intestine
The shortest part of the small intestine, where most chemical digestion takes place.
In humans, the duodenum is a hollow jointed tube about 25–38 cm
Submucosal Brunner’s glands, which can secrete mucus that neutralizes stomach acids.
Villous forms covered with columnar cells with a brush boarder.
Walls of duodenum
The duodenum wall is composed of a very thin layer of cells that form the muscularis mucosae.
The duodenum also regulates the rate of emptying of the stomach via hormonal pathways
Ileum
Small folds of mucosa to form villi to increase surface area to speed up diffusion
Epithelium of mucosa is simple columnar epithelium with microvilli brush border to increase surface area for the adsorption (attachment) of enzyme molecules and for the absorption of products of digestion.
One cell thick, short diffusion pathway, to allow rapid diffusion
Muscularis mucosa wafts villi increasing contact with food
Lacteal present in lamina proporia to absorb lipids (fatty acids and glycerol)
Blood capillaries to carry away products of digestion and maintain diffusion gradient
IDENTIFY L and label
Ileum
Identify O
Ileum
Intestinal villi - jejunum
The muscularis externa layer contains two layers of smooth muscle, an inner circular and outer longitudinal, for continuous peristaltic activity of the small intestine.
Identify Y
Intestinal villi- jejune
Identify and label P
sodium potassium pump
Colon
The large intestine completes absorption, and retrieves water and sodium from the luminal contents which become faecal residue.
It secretes large amounts of mucus, and some hormones, but no digestive enzymes.
Label R and identify
Colon
