Digestive system Flashcards
The four digestive processes explained
Ingestion – The process of taking food into the body.
Digestion – The process of breaking down food into its component parts in the stomach and small intestine.
Absorption – Occurs in the small intestine and large intestine – the process of transferring nutrients from the intestine into the bloodstream.
Excretion – Removal of indigestible material as faeces.
Order of the digestive tract
Oral Cavity
Oropharynx
Oesophagus
Stomach
Duodenum
Jejunum
Ileum
Caecum
Colon
Rectum
Anus
Name the four accessory digestive structures
Salivary Glands,
Liver,
Gall Bladder,
Pancreas
Describe four functions of the oral cavity
- Picking up food with the lips and tongue.
- Chewing to break up food into smaller boluses to aid swallowing.
- Lubrication of food with mucus and saliva.
- Digestion of carbohydrates in the mouth by salivary amylase (omnivores and herbivores only).
six functions of the tongue
- To aid ingestion
- To carry receptors for taste
- To form a bolus from food for swallowing
- Grooming
- Thermoregulation – flattening of the tongue and increased blood supply to the capillaries of the tongue allows saliva to evaporate and cooling of the body.
- Vocalisation – complex movements of the tongue allow an animal to vocalise.
The tongue is made of (1) allowing complex voluntary movement, with its root attached to the (2)
Striated muscle
Hyoid bone
the membrane which covers the gums is known as
the gingival membrane
incisor shape and function
small, chisel shaped with single root
Used for nibbling, cutting and grooming
Canine shape and function
pointed, curved, single root
grasping, gripping and piercing prey
Molar and pre molar
premolar<3>molar roots
Flatter surface with cusps
Shearing flesh with cusps,
flattened surfaces used for crushing and grinding.
saliva - structure and source
consists of 99:1 water:mucus
produced in salivary glands
function of soft palate
divide the naso/oro-pharynx
What system is the tonsil part of and what is its function
lymphatic system - protects the animal from disease
five steps of swallowing
- Food is rolled into a bolus by the tongue and is passed to the back of the mouth.
- The muscles of the pharynx contract, pushing the food bolus to the osophagus
- The epiglottis closes, preventing food entering the larynx.
- A wave of peristalsis pushes food down the osophagus.
- The epiglottis opens allowing respiration to begin again.
Function and location of esophagus
The osophagus carries food from the pharynx to the stomach. It lies dorsal and slightly to the left of the trachea. As it passes through the thorax it runs through the mediastinum, dorsal to the heart and between the lungs.
oesophogus structure
The osophagus is a tubular structure containing longitudinal and circular bands of smooth muscle. It is lined by stratified squamous epithelium.
structure and location of stomach within body
The stomach is a c-shaped sac-like organ which lies on the left side of the abdomen. it lies caudal to the diaphragm and cranial to the liver
stucture of stomach wall (4)
The stomach wall is lined by mucosa and has deep folds called rugae.
Within the wall are gastric pits containing:
- Goblet cells which produce mucus to protect the stomach wall from acid and digestive enzymes
- Chief cells which produce pepsinogen.
- Parietal cells which produce gastric (hydrochloric) acid.
three main functions of stomach
- To act as a reservoir for foods.
- To break up food and mix it with gastric juices
- To begin protein digestion
which movements take place within the stomach and their purpose
- Peristalsis – to propel food material through the stomach
- Rhythmic segmentation – to break up and mix food boluses.
processes which occur in the small intestine
digestion and absorbtion
The stomach breaks food down to a substance known as
Chyme
Small intestine consists of 3 parts;
Duodenum, Jejunum and Ileum
which structures empty into the first part of the small intestine
the pancreatic duct and the common bile duct
Describe parts of the ileocaecocolic junction
The ileocaecocolic (or ileocaecal) junction, at which location the ileum, caecum and colon meet.
- What is the function of the villi in the wall of the small intestine?
To improve efficiency of digestion and absorption of the nutrients from the small intestine by increasing the surface area.
properties of intestinal villi which aid with absorption
- Large Surface Area
- Excellent blood supply from a network of internal capillaries
- They have a thin layer of cells lining their wall
- Surface area is further increased by the presence of microvilli on the surface of the epithelial cells lining the villi.
Which two structures are located within the villi to transports absorbed substances
- Capillary Network – absorb carbohydrates and proteins to relay them to the hepatic portal vein
- Lacteal – to absorb fat in the form of chyle (the product of fat digestion) and relay it to the lymphatic system (specifically to the cisterna chyli).
- Name and describe (in terms of function) the four structures which make up the large intestine
- Caecum – a short blind ending tube. This is used for bacterial fermentation in hind-gut fermenting herbivores but has no significance in carnivores.
- Colon – made up of the ascending, transverse and descending. Water, vitamins and electrolytes are absorbed here.
- Rectum – found within the pelvic cavity, stores faeces before release.
- Anal Sphincter – controls the passage of faeces out of the body.
eight functions of liver
- Metabolism of carbohydrates and storage of glycogen
- Metabolism of proteins – including manufacture of plasma proteins, regulation of amino acids and production of urea from surplus amino acids.
- Metabolism of fat
- Bile formation which is subsequently stored in the gall bladder
- Destruction of old red blood cells
- Formation of new red blood cells
- Storage of vitamins (mainly fat soluble ones)
- Storage of iron
- Production of heat for the body
- Detoxification
where is the pancreas located
within the ‘U’ of the duodenum
function of bicarbonate
To neutralise the acid found in chyme.
function of trypsinogen
A precursor to trypsin which is activated in the small intestine.
function of typsin
Breaks down proteins and peptides into amino acids
function of lipase
converts fats into fatty acids and glycerol
function of amylase
breaks down starch into maltose
explain the process of trypsin
Active trypsin is not normally present in the pancreas, instead, the enzyme precursor trypsinogen is found in the pancreas. Activation of trypsinogen to trypsin is prevented in the pancreas by a trypsin inhibitor.
Trypsin becomes activated once it reaches its destination; the small intestine
where is bile made and stored
made in the liver and stored in gall bladder
function of bile
emulsify fat globules (to increase surface area for lipase to act)
function of mucus
Lubricates food and protects the stomach wall from auto-digestion.
function of hydrochloric acid
Begins the breakdown of proteins and creates a low pH to facilitate digestion
function of pepsinogen
A precursor to pepsin which is not active so prevents damage to the stomach wall, where it is produced
pepsin function
Breaks down proteins into peptides (is activated from pepsinogen in the acidic environment of the stomach).
