Ch 1 - Digestion and Absorption Flashcards
What is the most essential component of life?
Food
Why is food important for life?
The major components of our food are carbohydrates, proteins and fats. Vitamins and minerals are also required in small quantities. Food provides energy and organic materials for growth and repair of tissues.
What are the other two essential components in addition to food? Give reason
Roughage(Dietary Fibre) and Water
- Helps in easy digestion
- Prevents dehydration, regulates body temperature and helps in metabolic processes.
Define “Digestion”
The process of conversion of complex food substances to simple absorbable forms is called digestion
How is digestion carried out?
Digestive system through biochemical (enzymes) and mechanical methods(mouth and stomach)
What makes up the digestive system?
Alimentary Canal and Associated glands.
Explain about the Alimentary Canal
- Also called GI tract
- 7 compartments
- Anterior and Posterior
Explain about the human buccal cavity
- Set of teeth
- Tongue
Define “ Dentition”
Arrangement, type of teeth and number of a species set of teeth
What is a human being’s type of dentition?
Theocodont
Diphyodont
Heterodont
Define Theocodont
Each tooth is embedded in a socket of jaw bone.This type of attachment is called thecodont.
Define Diphyodont
Majority of mammals including human being forms two sets of teeth during their life, a set of temporary milk or deciduous teeth replaced by a set of permanent or adult teeth. This type of dentition is called diphyodont.
Define Heterodont
An adult human has 32 permanent teeth which are of four different types (Heterodont dentition), namely, incisors (I), canine (C), premolars (PM) and molars
(M).
Number of human teeth
32
Define “Dental Formula”
Arrangement of teeth in each half of the upper and lower jaw in the order I, C, PM, M is represented by a dental formula which in human is 2123/2123 .
Explain about the tongue
The tongue is a freely movable muscular organ
attached to the floor of the oral cavity by the frenulum
What holds the tongue to the floor of the oral cavity?
Frenulum
Explain “Pappilae”
The upper surface of the tongue has small projections called papillae, some of which bear taste buds.
Elaborate on the oesophagus
The oesophagus is a thin, long tube which extends posteriorly passing through the neck, thorax and diaphragm and leads to a ‘J’ shaped bag like structure called stomach. (Peristalsis)
Define Pharynx
The oral cavity leads into a short pharynx which serves as a common passage for food and air.
Define “Epiglottis” and “Glottis”
A cartilaginous flap called epiglottis prevents the entry of food into the glottis – opening of the wind pipe – during swallowing.
Define and explain the structure and location of stomach
The stomach, located in the upper left portion of the abdominal cavity, has four major parts – a cardiac portion into which the oesophagus opens, a fundic region, body
(main central region) and a pyloric portion
which opens into the first part of small intestine.
Which spinchter controls movement of food from oesophagus to stomach?
Gastro oesophagul spinchter
Define and explain the structure and location of small intestine
Small intestine is distinguishable into three regions, a ‘C’
shaped duodenum, a long coiled middle portion jejunum and a highly coiled ileum.
Which spinchter controls movement of food from stomach to small intestine?
Pyloric Spinchter
Define and explain the structure and location of large intestine
Ileum opens into the large intestine. It consists of caecum, colon and rectum. Caecum is a small blind sac which hosts some symbiotic micro-organisms. A narrow finger-like tubular projection, the vermiform appendix which is a vestigial organ, arises from the caecum. The caecum opens into the colon. The colon is divided into four parts – an ascending, a transverse, descending part and a sigmoid colon. The descending part opens into the rectum which opens out through the anus.
Why is caecum called “blind sac”?
The caecum is called blind sac because caecum looks like a sac which has sphincter at the ileocaecal junction and it remains closed and is invisible.
Which part of the large intestine is called a vestigial organ and why?
Vermiform appendix because it’s useless.
Who hosts symbiotic microorganisms and why?
Caecum
-helps in indigestion
Describe the transverse section of the gut or the alimentary canal.
4m+1m(diagram)
_________ epithelium has ___________cells that produce____________ for ____________.
Mucosal
goblet
mucous
lubrication
How many salivary glands are there in body?
6 (3p)
Name them and where are they located?
Parotid gland - cheeks
Submaxilliary/Submandibular - Lower jaw
Sublingual - under tongue
What do salivary glands secrete ?
saliva…duh 🙄
What is the largest gland in the body?
Liver
How much does liver weigh?
1.2-1.5kg
Where is liver located?
In abdominal cavity under diapghram
How many lobes does the liver have?
2
Liver Question:-
—————-is known as the ————- and ——————unit of the liver.
Hepatic lobules
functional
structural
Each of the hepatic lobule is covered with ————–.Define ———-.
Glisson’s capsule is a thin connective tissue sheath arranged in the form of chords.
What does the liver secrete?
Bile juice
Who in the liver produces the bile juice?
Hepatic cells
Where is the bile stored? And define.
Gall bladder is a muscular bag like structure that stores bile juice.
How is bile transported to gall bladder?
Through hepatic duct
The————duct and the ———duct(also known as————duct) form the common bile duct.
hepatic
bile
cystic
The bile duct and ——————-duct form the ————————-and open into the —————— and is guarded by————–spinchter
pancreatic
common hepato pancreatic duct
duodenum
oddi
Define pancreas and what are the two parts of pancreas?
The pancreas is a compound elongated
organ situated between the limbs of the ‘U’ shaped duodenum. The parts are exocrine and endocrine parts.
What does endocrine and exocrine part secrete?
Endo- Hormones like insulin and glucagon
Exo- pancreatic juices that has enzymes
In what medium is pancreatic juice present?
Alkaline medium
Through what methods can digestion happen?
- Mechanical
2. Biochemical
What are two main functions of buccal cavity?
- Mastication of food
2. Swallowing of food
What does the teeth and tongue do?
mastication of food, churning, mixing it with saliva
Function of mucous on saliva
- Lubrication of food
2. adhere masticated food particles into bolus
What is deglutition?
Swallowing of food into the pharynx from mouth
What are the 2 main components in saliva?
- Electrolytes[Ca+,Cl-,HCO3-]
2. Enzymes such as Salivary amylase and Lysozyme
Function of Salivary Amylase
1.upon hydrolytic action, is a carbohydrate splitting enzyme
Function of Lysozyme
prevents bacterial infections in mouth
At what pH should salivary amylase be to digest carbohydrates?
6.8
What percent of carbohydrates get digested in mouth.?
30%
Define Peristalsis
Successive muscular contractions of oesophagus to push food down to stomach
Name spinchter controls the passage of food
into the stomach.
Gastro-oesophagul spinchter
Which layer forms glands in the stomach?Name the gland.
Mucosal layer
Gastric Glands
What are types of cells in gastric glands? Explain.
(i) mucus neck cells which secrete mucus;
(ii) peptic or chief cells which secrete the proenzyme pepsinogen
(iii) parietal or oxyntic cells which secrete HCl and intrinsic factor.(factor essential for absorption of vitamin B12).
Function of Intrinsic Factor
Absorption of Vit-B12 in stomach
How many hours does it take for digestion in stomach?
4-5 hours
Mechanical method of digestion in stomach
The food mixes thoroughly with the acidic gastric juice of the stomach by the churning movements of its muscular wall and is called the chyme.
Define “Chyme”
Food in stomach after mixing with digestive juices.
What activates Pepsinogen and into what?
HCl into Pepsin
Is pepsin a proteolytic enzyme?
Yes
How does pepsin digest proteins?
Pepsin converts proteins into proteoses and peptones (peptides).
What do mucuos and bicarbonates do in stomach?
The mucus and bicarbonates present in the gastric juice play an important role in lubrication and protection of the mucosal epithelium from excoriation by the highly concentrated hydrochloric acid.
What is the optimum pH for HCl to convert pepsinogen?
1.8
Function of Rennin
Rennin is a proteolytic enzyme found in gastric juice
of infants which helps in the digestion of milk proteins.
Are lipases present in stomach?
Yes, in small amounts
Mechanical method of digestion in small intestine
Various types of movements are generated by the muscularis layer of the small intestine. These movements help in a thorough mixing up of the food with various secretions in the intestine and thereby facilitate digestion.
What are the secretions found in small intestine?
The bile, pancreatic juice and the intestinal juice are the
secretions released into the small intestine.
How does pancreatic and bile juice go into duodenum?
Common Hepato Pancreatic Duct
Constituents of Pancreatic juice
The pancreatic juice contains inactive enzymes – trypsinogen, chymotrypsinogen, procarboxypeptidases, amylases, lipases and nucleases.
How does digestion happen with the help of pancreatic juice. Explain
Trypsinogen is activated by an enzyme, enterokinase, secreted by the intestinal mucosa into active trypsin, which in turn activates the other enzymes in the
pancreatic juice.
Define Entirokinase
enzyme secreted by intestinal mucosa which activate trypsinogen.
Constituents of Bile juice
The bile released into the duodenum contains bile
pigments (bilirubin and bili-verdin), bile salts, cholesterol and phospholipids but no enzymes.
What are the 2 main functions of bile?
Bile helps in emulsification of fats, i.e., breaking down of the fats into very small micelles. Bile also activates lipases
How is intestinal juice formed?
The intestinal mucosal epithelium has goblet cells which secrete mucus. The secretions of the brush border cells of the mucosa along with the secretions of the goblet cells constitute the intestinal juice.
What is succus entericus?
intestinal juice
Constituents of intestinal juice
This juice contains a variety of enzymes like
disaccharidases (e.g., maltase), dipeptidases, lipases, nucleosidases, etc.
What do mucuos and bicarbonates do in small intestine?
The mucus alongwith the bicarbonates from the pancreas protects the intestinal mucosa from acid as well as provide an alkaline medium (pH 7.8) for enzymatic activities.
What is the name of the submucosal gland in duodenum that has similar property to mucous and bicarbonates?
Brunner’s gland
How does Pancreatic juice digest proteins?
Proteins
Peptones
Proteoses ➡️ Trypsin/Chymotrypsin/Carboxypeptidases ➡️ Dipeptides
How does Pancreatic juice digest carboydrates?
Carboydrates[Polysaccharides]➡️Pancreatic Amylase➡️Disaccharides[Maltose]
How does Pancreatic juice digest fats?
Fats➡️Lipase[help of bile]➡️Diglycerrides/Monoglycerides
How does Pancreatic juice digest nucleic acids?
Nucleic acids➡️nucleases➡️Nucleotides/Nucleosides
How does Intestinal juice act on partially digested substances?
Dipeptides➡️Dipeptidases➡️Amino acids
Maltose➡️Maltase➡️Glucose+Glucose
Sucrose➡️Sucrase➡️Glucose+Fructose
Lactose➡️Lactase➡️Glucose+Galactose
Di/Monoglycerides➡️Lipase➡️Fatty Acids+Glycerol
Nucleosides/Nucleotides➡️Nucleosidases/Nucleotidases➡️Sugars+Bases
Where does complete site of digestion happen?
Duodenum
Where does complete site of absorption happen?
Jejunum and Ileum
Main 2 functions of large intestine
- Absorption of water,salts,minerals,drugs
2. Secretion of mucous to adhere into faeces
How does the undigested and unabsorbed material go to caecum? Main function
Ileo-caecal valve prevents backflow of faecel matter
Note:-
The activities of the gastro-intestinal tract are under neural and hormonal control with the help of CNS and Local centres
Note:-
Calorie - Unit of heat energy
Define”Absorption”. What are the three types of absorption?
Absorption is the process by which the end products of digestion pass through the intestinal mucosa into the blood or lymph. It is carried out by passive, active or facilitated transport mechanisms.
Explain Facilitated transport mechanism
Small amounts of monosaccharides like glucose, amino acids and some electrolytes like chloride ions are generally absorbed by simple diffusion. The passage of
these substances into the blood depends upon the concentration gradients. However, some substances like glucose and amino acids are absorbed with the help of carrier proteins. This mechanism is called the facilitated transport.
Explain Active transport mechanism
Transport of water depends upon the osmotic gradient. Active transport occurs against the concentration gradient and hence requires energy. Various nutrients like amino acids, monosaccharides like glucose,
electrolytes like Na+ are absorbed into the blood by this mechanism.
Explain Passive transport mechanism
- Fatty acids and glycerol being insoluble, cannot be absorbed into the blood.
- They are first incorporated into small droplets called micelles which move into the intestinal mucosa.
- They are re-formed into very small protein coated fat globules called the chylomicrons.
- They are transported into the lymph vessels (lacteals) in the villi.
- Lymph vessels ultimately release the absorbed substances into the blood stream.
What all does the stomach and mouth absorb?
Mouth - Certain drugs
Stomach - Alcohol,water,simple sugar, Vit B12
Define Assimilation
The absorbed substances finally reach the tissues which utilise them for their activities. This process is called assimilation.
Define Egestion
The process of elimination of undigested food out of the body is called egestion.
Define Ingestion
The process of taking food, drink, or another substance into the body by swallowing.
Note:-✨
The digestive wastes, solidified into coherent faeces in the rectum initiate a ✨neural reflex ✨causing an urge or desire for its removal. The egestion of faeces to the outside through the anal opening (defaecation) is
a ✨voluntary process✨ and is carried out by a
✨mass peristaltic movement.✨
Inflammation of Alimentary Canal happens due to
Viral and Bacterial infections
Other infections happen due to
Parasites in small intestine[tapeworm,roundworm]
Jaundice affects which organ and its symptoms. How is it caused?
Liver
Yellowing of eyes and skin
Deposit of Bile Pigments
Define “Vomitting”. How is it controlled?Is it a reflex action?
Ejection of stomach contents
Controlled by vomit centre in medulla
Yes
What happens when you get diarrhoea?
Reduced absorption of food
Abnormal bowel frequency
increased liquidity of faeces
What happens when you get constipation?
faeces retained in colon
irregular bowel movement
What happens when you get indigestion?
food does not get digested
feeling full
inadequate secretion of enzyme,spice,overeating
PEM
Protein Energy Malnutrition
What are two main diseases caused by PEM?
- Kwashiorkar-only protein deficiency[toddlers] - some fat left/extensive oedema and swelling
- Marasmus - protein and calorie deficiency[enfants]-no growth and thinning of body
