Structures and Functions of the Digestive System: A Comprehensive Overview

This presentation provides a detailed overview of the structures and functions of the digestive system, including chemical and mechanical digestion. It also covers the constituent food groups of a balanced diet. The presentation is based on research studies and academic sources.

Biology
Presented by:

Structures and Functions of the
Digestive System
 Mouth
– Ingests food
– Chemical analysis of
carbohydrates
– Initiates the breakdown of
lipids through lingual lipase
– Food is moved to the pharynx
 Pharynx
– Pushes food from the mouth
to the oesophagus (Kong and
Singh, 2008).

Structures and Functions of the
Digestive System…
Stomach
– Mixes and churns food with
gastric juices to form chime
– Commences chemical
breakdown of proteins
– The food (in the form of
chime) is released to the
duodenum
– Absorbs some fat soluble
substances such as aspirin
(Kong and Singh, 2008).
 Oesophagus
– Found in the throat near the
trachea
– Receives food once
swallowed
– Delivers food to the
stomach through peristalsis
– Lubricates food and
passageways
– Delivers food to the
stomach (Kong and Singh,
2008).

Structures and Functions of the
Digestive System…
 Pancreas
– Secrets digestive enzymes into the
duodenum
– The enzymes breaks down protein,
carbohydrates and fats
– Produces insulin, and secrets it to
the bloodstream
 Liver
– Breakdown of chime from the
small intestines
– Secretes bile into small
intestines, which aids in
digesting fat
– Detoxifies dangerous chemicals
 Small intestines
– Consists of the ileum, jejunum, &
duodenum
– Combines chime with digestive
secretions
– Thrusts food at a gradual pace to
allow for digestion and absorption
– Absorbs analysis of the outcomes
of carbohydrates, proteins, nucleic
acids and water
– Carries out mechanical digestion
through segmentation
– Provides optimal conditions for
enzymatic reactions (Kong and
Singh, 2008).

Structures and Functions of the
Digestive System…
 Large intestines (colon)
– Further breaks down food deposits
– Absorbs the remaining water,
electrolytes and vitamins made by
eccentric bacteria
– Moves food to the rectum
– Eliminates stool
 Anus
– Lining of its upper area detects
rectal contents
– Its sphincter muscles allows the
control of stool
– The pelvic floor muscle stops the
elimination of stool when its
unnecessary.
 Gall bladder
– Provides and distillates bile
– Secretes bile into the small
intestines to aid in
absorbing and digestion of
fats
 Rectum
– Connects colon to the anus
– Receives faeces from the
colon and holds it until
elimination
(Kong and Singh, 2008).

Chemical Digestion
 Involves enzyme secretion throughout the whole
digestive tract
 Chemical digestion is responsible for the breakdown of
various nutrients such as carbohydrates into much
smaller parts.
 Begins in the mouth, where salivary glands secrete saliva
into the mouth.
 Digestive enzymes in the mouth:
– Salivary amylase – breaks down polysaccharides
 Digestive enzymes in the small intestines:
– Lactase - digests lactose (Bakke, Glover,and
Krogdahl, 2010)

Mechanical Digestion
 Physical breakdown of food.
 Takes place in different locations of the
digestive system:
– Mouth
– Esophagus
– Stomach – muscular contraction actions of
the stomach
– Small intestines – secretes bile and enables
peristalsis.

Optimal Conditions Enzymatic
Action
 pH
– pH of an electrolyte have multiple impact on the enzymatic
action
– Extremely High or low pH values leads to poor enzymatic
action
– Optimal pH for Salivary amylase 4.6-5.2
 Temperature
– The rate of enzymatic reaction increases as temperature
increases to a optimum level and then decreases with each
further temperature increase
– Optimal temperature: 37.5 digress Celsius

Constituent Food Groups of a
Balanced Diet
 Carbohydrates
– Supplies the body with glucose; source of energy
– Obtained from plant sources such as corn, rice, wheat etc
 Fats
– Help in the body synthesis of fat-soluble vitamins
– Obtained from foods such as milk, egg and butter etc
 Proteins
– Helps in the development of muscles, hair and skin
– Obtained from both animal (fish, eggs, cheese, and lean meat) and plant sources
(ground-nuts, maize, whole wheat etc)
 Vitamins
– Help maintain healthy teeth, bones, mucus membrane and skin
– Sources include most fruits, and vegetables
 Minerals
– Help in strong bones to transmitting nerve impulses
– Sources include green vegetables, dairy and meat products (British Nutrition Foundation,
n.d).

References
Bakke, A.M., Glover, C. and Krogdahl, Å., 2010. Feeding,
digestion and absorption of nutrients. In Fish
physiology (Vol. 30, pp. 57-110). Academic Press.
British Nutrition Foundation, n.d. [online]. Available from:
https://www.nutrition.org.uk/healthyliving/healthydiet.html
[Accessed 26 December 2018].
Kong, F. and Singh, R.P., 2008. Disintegration of solid
foods in human stomach. Journal of food science, 73(5),
pp.R67-R80.