Digestive system Flashcards
(18 cards)
Peristalsis
Peristalsis is the involuntary contraction and relaxation of longitudinal and circular muscles throughout the digestive tract.
Moves food along the gastrointestinal (GI) tract.
The Oesophagus
A straight muscular tube connecting the mouth to the stomach.
Made up of smooth muscle cells that contract in a wave-like motion to push food down.
These contractions are called peristalsis.
STOMACH(structures)
A muscular sack.
It has inner folds (rugae) that increase the surface area of the stomach.
STOMACH(functions)
Churns and grinds together the bolus into smaller pieces (physical digestion).
Food is mixed with gastric juices (HCl and enzymes) secreted by the stomach walls (for chemical digestion).
HCl helps break down food and kills bacteria that come along with the food.
STOMACH(enzymes)
Gastric amylase
Pepsin
SMALL INTESTINE(Structure)
Three sections:
Duodenum
Jejunum
Ileum
Structure:
Thin, muscular tube
DUODENUM
The first part of the small intestine.
Lined with mucous to protect against acidic stomach content (chyme).
Chyme is neutralised as soon as it enters the duodenum by bicarbonate
BILE
Greenish-yellow fluid.
Produced in the liver.
Stored in the gallbladder.
Main function: break up (emulsify) large globules of fat into smaller globules, increasing the surface area for lipase to start digestion.
DUODENUM (enzymes)
Trypsin & chymotrypsin (proteases) break down polypeptides into amino acids
Pancreatic amylase breaks down carbohydrates to glucose
Lipase breaks down lipids to fatty acids & glycerol
All of these enzymes are released into the duodenum from the pancreas.
JEJUNUM + ILEUM
Where the majority of digested food particles (glucose, amino acids, glycerol and fatty acids) are absorbed into the bloodstream.
LARGE INTESTINE
Water and vitamins are absorbed from the undigested food.
Solidifies any leftover materials, creating waste.
Waste is then stored in the rectum and egested through the anus.
ABSORPTION
the diffusion of digested food particles from the small intestine into the bloodstream.
To increase the rate of absorption, the inside of the small intestine is lined with finger-like projections called villi.
VILLI (adaptions)
Folded = increased surface area = increased rate of absorption.
Only one cell thick, so digested food particles have a reduced distance to the bloodstream.
Each villus also has microvilli, which further increase surface area.
Each villus has its own blood supply.
VILLI(structure)
Blood vessels - absorb glucose and amino acids
Lymph vessel - (called lacteals), absorbs fatty acids and glycerol
Microvilli
Each cell of a Villi has microvilli, further increasing surface area for absorption of nutrients into the bloodstream.
Assimilation
This is the process where the digested nutrients are delivered to, and used by cells.
Upon being absorbed into the bloodstream, all the blood is sent to the liver via the hepatic portal vein – the liver acts as a distribution centre of our nutrients it decides how and when the nutrients are released to be utilised by our body
EGESTION
The act or process of discharging undigested or waste material from an organism; specifically : defecation.
Normally, faeces are made up of 75 percent water and 25 percent solid matter.
About 30 percent of the solid matter consists of dead bacteria;
Another 30 percent consists of indigestible food matter such as cellulose;
10 to 20 percent is cholesterol and other fats;
The brown colour of faeces is due to the action of bacteria on the breakdown of hemoglobin (red blood cells).
Liver
largest gland in the body. Undertakes many key processes:
Blood Sugar Level Control: it has the ability to store glucose as glycogen; or alternatively, release stored glucose. Both process are under the control of two hormones produced by the pancreas – Insulin and Glucagon
Deamination: removal of the toxic amine group from amino acids – minimises the build up of toxic ammonia in the body
Detoxification: processes most toxins and poisons and drugs
Stores important vitamins and minerals and iron
