Digestive System Flashcards
Define animal nutrition?
Animal nutrition is the process by which food is taken in for make use in different body function
Define heterotrophic nutrition?
Process by which the animal obtain organic food molecules by ingesting other organisms or by substance derived from other organisms.
State the 2 types of heterotrophic nutrition
Holozoic nutrition
Symbiosis
State some heterotrophic organisms
Animals
Fungi
Majority of bacteria
What is holozoic nutrition?
It is a types of heterotrophic nutrition where animals ingest food for digestion into their alimentary canals
State the 5 main stages of holozoic nutrition
Ingestion Digestion Absorption Assimilation ( utilization) Elimination (Egestion)
Ingestion
1st stage
Act of feeding or eating happens
Different food sources
Different modes of ingestion ( feeding mechanism)
Different types of diet depending on their env
State 4 feeding mechanism of animals
Filter feeders
Fluid feeders
Substrate feeders
Bulk feesders
Examples for filter feeders and mechanism used by them
Bivalves such as clams and oysters
Capturing and trapping mechanism are used
Examples for fluid feeders and state the fluid which they feed
State an adaptation seen in them for an efficient feeding
Mosquito - human blood
Aphids - phloem sap if plant
Bees and humming bird - honey from flower
Well adapted mouth part
Examples for substrate feeders and mention their substrate to which they feed
Leaf miner caterpillar - eating through soft tissue of teeth
Maggots ( fly larvae ) - burrow into animal carcasses
Examples for bulk feeders and adaptations seen in bulk feeders
Most animals including human
Different adaptations to tear food and capture prey
( jaws, teeth, tentacles, claws,poisonous fangs)
Digestion
Food is broken down into very small molecules which are small enough to pass through the membrane and enter cells of organisms
Two types of digestion with examples
What happens to the food during each type of digestion
( During mechanical digestion, food is broken down in to smaller fragments thus increase the surface area for efficient chemical digestion )
( During chemical digestion enzymes break bonds in large molecules into small molecules.)
Differentiate chemical and mechanical digestion
During mechanical digestion, food is broken down in to smaller fragments thus increase the surface area for efficient chemical digestion.
During chemical digestion enzymes break bonds in large molecules into small molecules.
State the stages of holozoic nutrition which occur after digestion
Absorption
Assimilation
Elimination
Absorption
In this stage, the animal’s cells take up small molecules
. e.g.simple sugars, amino acids
State the stage of holozoic nutrition which occur outer to the alimentary canal?
Assimilation
Assimilation
Assimilation is the process of utilization of absorbed nutrients for various functions of the body.
Elimination
this process undigested materials are passed out from the alimentary canal.
Define symbiosis
This is an ecological relationship between organisms of two different species that live closely together.
3 types of symbiotic relationships
Mutualism
Parasitism
Commensalism
Mutualism
It is a close association between two living organisms of different species which benefits both partners.
e. g. - Cellulose digesting microorganisms in Ruminants and Termites
Parasitism
It is a close association between two living organisms of different species which is beneficial to one (parasite) and harmful to the other (host).
e.g. –Tape worm and humans, Lice and humans
Commensalism
It is a close association between two living organisms of different species which is beneficial to one and does not affect the other (neither harmful or beneficial)
e.g.- Barnacles attached to whales
State the structures in the alimentary canal of human
The alimentary canal consists of the following parts: oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, rectum and anus
State 3 associated glands of human digestive system
The associated glands include salivary glands, pancreas and liver.
State 3 structures in the oral cavity
Oral cavity consists of the tongue, teeth and salivary glands
What are the stages of holozoic nutrition which occurs in the mouth cavity
Ingestion and initial steps of digestion are carried out in the oral cavity.
In digestion
Both chemical and mechanical digestion takes place
State the mechanical digestion which occurs in the mouth
Food is cut, mashed and ground by different types of teeth with different shapes.
This makes it easier to swallow food and increase the surface area for digestion.
State the chemical digestion which occurs in the mouth
Salivary amylase: Chemical digestion of polysaccharides (e.g. starch) into smaller polysaccharides and disaccharide maltose.
How does the release of saliva occur when food enters the mouth
Releasing saliva into the oral cavity occurs when food enters the oral cavity due to a nervous reflex.
When would salivation occur
Releasing saliva into the oral cavity occurs when food enters the oral cavity due to a nervous reflex.
Saliva is also released into the mouth before food is ingested due to various other stimuli. e.g. sight, odor of food, etc.
State the composition of saliva?
Saliva contains water, amylase, mucus In addition to that, saliva composed of buffers and anti microbial components.
What is the composition of mucus
a viscous mixture of salts, cells and slippery glycoprotein called mucins
Function of saliva
Functions of the saliva
• Salivary amylase: Chemical digestion of polysaccharides (e.g. starch) into smaller polysaccharides and disaccharide maltose.
- Water: Liquefy food and provide watery medium for chemical digestion. Aids in taste reception.
- Mucus: Lubrication of food which makes it easier for swallowing. Clean the mouth and protects the lining of the mouth from abrasion.
- Antimicrobial substances such as immunoglobulin and lysozymes: Protect against bacteria that enter the mouth.
- Buffers prevent tooth decay by neutralizing acid
State 2 enzymes found in the mouth
Salivary amylase (ptyalin) Lysozyme
State 2 anti microbial component in the mouth
Immunoglobulin
Lysozyme
State 4 types teeth
incisors, canines, premolars and molars.
Importance of tongue
Helps to mix the food with saliva
make bolus of food that makes easier for swallowing.
Then helps to push the bolus into the posterior part of the oral cavity and into the pharynx.
Helps in speech
Taste buds in the tongue helps in taste sensation
State the common passage of respiratory and digestive tract?
Pharynx
3 types of pharynx and their location
Nasopharynx
Opens to the nasal cavity
Oropharynx
Opens to the oral cavity
Laryngopharynx
Opens to the larynx
What is the name of the food which passes through the esophagus from the mouth cavity
Bolus
State the long tube which connects the pharynx and the stomach
Esophagus
Location of esophagus
It is located in the thoracic cavity
State the two types of muscles in the esophagus
Smooth muscle tissue
Skeletal muscles tissue
What is peristalsis
alternative wave of rhythmic contractions and relaxations of the smooth muscles lining the esophagus.
State the process which helps in passing the food bolus through the esophagus into the stomach?
And how?
Peristalsis
During this process the food bolus is pushed along the esophagus by the alternative wave of rhythmic contractions and relaxations of the smooth muscles lining the esophagus due to the peristalsis
Location of skeletal and smooth muscle tissue of esophagus with their function
skeletal muscles are located towards the uppermost part of the esophagus and these muscles function during swallowing.
The rest of the esophagus consists of smooth muscles which are involved in the process called peristalsis.
State 2 types of smooth muscles in the wall of alimentary canal
Longitudinal muscle
Circular muscle
Describe the anatomy of the stomach
The stomach is a J- shaped dilated sac. In stomach externally lesser and greater curvature can be identified.
Stomach is present in the abdominal cavity, immediately below diaphragm left to the liver.
Stomach is present between the esophagus and the duodenum
The inner surface of the stomach is highly folded.
The most muscular wall of the alimentary canal is present in the stomach.
Therefore stomach wall is very elastic.
Distal part of the stomach connects with the small intestine.
Sphincters are found at the junctions between esophagus and stomach (cardiac sphincter) and stomach and the small intestine(pyloric sphincter). They are made up of rings of circular smooth muscles having a hole in the middle.
These sphincters help to regulate the passage of materials between these organs.
The inner surface of the stomach is highly folded into temporary foldings into the lumen. They become flat when food enters into the stomach allowing expansion of the stomach.
The inner surface of the stomach also contains large number of pits that leads to gastric glands.
Gastric glands contain three types of cells: mucus cells, chief cells and parietal cells.
State 3 muscle layers and 4 regions in the stomach
Longitudinal muscle layer
Circular muscle layer
Oblique muscle layer
Cardia, fundus, body, Pylorus
Chemical and mechanical digestion in stomach
The gastric glands of the stomach secrete gastric juice.
The gastric juice mainly consists of mucus, pepsinogen and HCl.
Mucus and pepsinogen (inactive form of pepsin ) are secreted by mucous cells and chief cells respectively.
The parietal cells release hydrogen ions and chloride ions separately into the stomach lumen where HCl is formed. This HCl maintains an acidic ph in the stomach at around 2.
In the stomach food is mixed with gastric juice forming chyme (partially digested semisolid, acidic, food mass).
Pepsinogen is initially converted into pepsin by HCl.
These activated pepsin help to activate remaining pepsinogen molecules.
This activated pepsin initiates the chemical digestion of proteins in the stomach. Where Proteins are hydrolyzed to small polypeptides by pepsin.
The churning action of the stomach facilitates the chemical digestion.
This is a series of muscle contraction and relaxation. This process mixes the swallowed food with gastric juice.
• Mechanical digestion of food by churning action due to muscular contraction.
What is chyme
In the stomach food is mixed with gastric juice forming chyme
(partially digested semisolid, acidic, food mass).
What is the function of intrinsic factor
Helps absorption of vitamin B12
Which is an essential nutrient for the production RBC
Several adaptations shown by the stomach to protect its inner lining from self digestion
The stomach lining is protected from the digestion of HCl and pepsin in several ways:
Enzymes are secreted in to the lumen as an inactive enzyme;
Gastric glands secrete mucus that protect against self-digestion of the stomach lining ;
Every three days, cell division adds a new epithelial cell layer which replaces the destroyed/ damaged cells in the lining of the stomach.
Functions of stomach
- Act as a temporary reservoir for food due to high convolution and very elastic wall.
- Mechanical digestion of food by churning action due to muscular contraction.
- Produce gastric juice which starts the chemical digestion of proteins to polypeptide by pepsin
- Absorption of some materials such as water, alcohol and some drugs
- Non specific defense-HCl kills microbes
- Small jets of gastric contents push out through pyloric sphincter as chyme
- Secretion of gastrin hormone which regulates digestion in the stomach.
Describe the three regions of small intestine
The duodenum: C shaped curve, around the head of the pancreas.
The jejunum is middle part of the small intestine. The ileum is the terminal part of the small intestine.
How is the area of small intestine increased and the reason for this increment in area
For effective absorption, the surface area of the intestinal wall has been increased with three structural modifications:
heavy permanent circular foldings,
finger like projections called villi in the intestinal wall
and finger like microscopic projections called microvilli in the epithelial cells of the villi. These micro villi are exposed into the intestinal lumen, it gives the appearance of brush (brush border).
Name 2 sphincter in the stomach and there function
Cardiac sphincter
Passes food bolus from the esophagus to the stomach
Pyloric sphincter
Passes chyme from stomach to small intestine
State the secretions with which the chyme is mixed
The chyme is mixed with secretions of glands in intestinal wall and secretions of pancreas and liver.
What does the secretions from the wall of duodenum contain
enzymes such as Disaccharidases, Dipeptidases, Carboxypeptidases, Aminopeptidases, Nucleotidases, Nucleosidases and Phosphotases. Some of these enzymes are secreted to the lumen and others are bound to the surface of the epithelium.
State 2 hormones secreted by the duodenum and there function
Two hormones namely cholecystokonin and secretin secreted by duodenum stimulates the release of pancreatic juice and the bile.
Enzymes in pancreatic juice
Pancreatic juice contains enzymes such as Trypsin, Chymotrypsin , Pancreatic amylase , Pancreatic Carboxypeptidases, Pancreatic Nucleases and Pancreatic Lipases. In addition it also contains bicarbonates.
Constituent of bile
Bile salt
Bile pigments
State the nutrients which are absorbed across the epithelium as active or passive
Transport of the nutrients across the epithelium may be active or passive.
Fructose is absorbed by facilitated diffusion.
Amino acids, small peptides, vitamins, and most glucose molecules are actively transported into the epithelial cells.
What happens to the nutrients absorbed from epithelial cells of small intestine
Then these nutrients from the epithelial cells are transported into the blood capillaries in the villi.
Those blood capillaries are converged into the hepatic portal veins.
These nutrients are carried in to the liver via the hepatic portal veins.
From the liver, this nutrient filled blood is transported into the tissues
State the other pathway in which some products of fat digestion is transported
But absorption of some products of fat digestion takes place in a different pathway:
Fatty acids and monoglycerides are absorbed into the cell through microvilli.
Within the cells triglycerides are reformed and they are incooperated into water soluble globules called chylomicrons.
These chylomicrons are transported into the lacteal and then into the blood vessels through lymph.
Then they are transported throughout the body via the circulatory system.
State another substance absorbed in the small intestine other than nutrients
In addition to nutrient absorption, recovery of water and ions mostly occur in the small intestine.
In addition to the water intake (about 2 L) digestive juices add more water (about 7 L) into the small intestine.
Most of this water is reabsorbed via osmosis.
State the organ where highest amount of water absorption occur
Small intestine
State the 3 regions in large intestine and describe each location
Cecum ,colon ,rectum
The small intestine is connected to the large intestine at a ‘T’ shaped junction.
One arm of the ‘T’ junction is colon and the other arm is a small pouch called cecum.
A finger like projection in the cecum is called the appendix.
The colon leads to the rectum and anus.
Function of each regions in large intestine
• The colon: completes the reabsorption of water,
synthesize some Vitamin B complexes,
Vitamin K and folic acid with the help of microbes
move feces (consists of undigested matter such as fibres) along the colon by peristalsis.
• The rectum stores feces until they are eliminated.
Presence of two sphincters between the rectum and anus can regulate feces movement.
Cecum is important for fermentation of indigested materials by microbes, especially in animals that eat large amount of plant matter.
Description on the external appearance of the pancreas
The pancreas is a pale grey gland which consists of a broad head, a body and a narrow tail.
Head is in the curve of the duodenum.
What does the exocrine and the endocrine part of the pancreas consist of
The exocrine part consists of a large number of lobules made up of small acini
Endocrine part of the pancreas is the islets of Langerhans, which consist of group of specialized cells.
What are the secretions secreted by the exocrine and the endocrine part of the pancreas
Exocrine part of the pancreas secretes pancreatic juice.
Endocrine part secrete hormones, glucagan and insulin which are involved in glucose homeostasis.
What is the constituent of pancreatic juice
The components of the pancreatic juice are bicarbonate,
carbohydrate digesting enzymes (pancreatic amylase),
pancreatic lipase,
nucleases
inactive form of protein digesting enzymes(trpsinogen and chymotrypsinogen pancreatic carboxypeptidase ).
Describe the histological structure of pancreas
Pancreas consists of a large number of lobules made up of small acini, the walls of which consist of secretary cells.
Each lobule is drained by a tiny duct and these unite eventually to form the pancreatic duct.
pancreas is also composed of the islets of Langerhans, which consist of group of specialized cells. They do not have ducts.
State the largest gland and the second largest organ in the body
Liver
Describe the structure of liver
- external appearance
- internal structure of liver (liver lobule)
- blood supply
- movement of blood out from liver and bile formation in liver
Its upper and anterior surfaces are smooth and convex.
Its posterior surface is irregular in outline.
Liver contains four lobes. Each lobe is made up of tiny hexagonal shape lobules which are the functional unit. These lobules are made up of cuboidal cells called hepatocytes which are arranged in pairs of columns radiating from a central vein. Between two pairs of column of cells there are sinusoids . Hepatic macrophages (Kupffer cells) are found in the lining of the sinusoids.
Sinusoid containing mixture of blood from the tiny branches of the portal vein and hepatic artery.
This arrangement allows venous blood (high concentration of nutritional materials) to mix with arterial blood and come into close contact with liver cells.
Blood drains from the sinusoids into central veins
which joins with veins from the other lobules, forming larger veins
and eventually the hepatic vein.
Bile canaliculi run between columns of liver cells.
Canaliculi join up to form larger bile canals.
What the ducts found in the corners of the hexagonal shaped lobule of liver
In the corner of the hexagonal structure a branch of hepatic artery, a branch of the hepatic portal vein and intra lobular bile duct can be found.
Functions of liver
perform functions such as metabolism of carbohydrates, fats and proteins,
detoxification of drugs and toxic substances,
defense against microbes,
some hormone inactivation and
heat production.
The liver secretes bile
bile contains bile salts which act as emulsifiers that help in fat digestion and absorption
it regulates the distribution of nutrients to the rest of the body.
Excess glucose is stored as glycogen in the liver cells. Glycogen deposition and break down in the liver cells are regulated by insulin and glucagon hormones.
Fat soluble Vitamins (A,D,E and K) and some water soluble vitamins (B12), iron and copper are also stored in liver.
Hormone secreted in the stomach and function of it
Gastrin
gastrin stimulates the production of gastric juice at the stomach.
Hormones secreted in the duodenum and it’s function
Fatty acids and amino acids in the chyme trigger the release of Cholecystokinin and Secretin from the duodenum.
Cholecystokinin triggers release of bile from the gall bladder and digestive enzymes from the pancreas.
Secretin stimulates the release of bicarbonate from the pancreas.
Bicarbonate neutralize the chyme received from the stomach
State what happens when chyme is rich in fat
food digestion in the stomach slows down due to high levels of Cholecystokinin and Secretin secreted by duodenum.
These hormones act on the stomach and inhibit peristalsis and gastric juice secretion.
