Download Human Nutrition session 4

Human Nutrition
Supervision
Prof. Dr. Mervat Salah
Intended Learning Outcomes
-
By the end of this lecture, students will
have a general overview on roles of the
gastrointestinal (GI) tract .
The primary roles of the gastrointestinal (GI) tract
are to
(1) extract macronutrients, protein, carbohydrates, lipids
,water, and ethanol from ingested foods and beverages;
(2) absorb necessary micronutrients and trace elements;
and
(3) serve as a physical and immunologic barrier to
microorganisms, foreign material, and potential antigens
consumed with food or formed during the passage of food
through the GI tract. In addition to its primary roles, the GI
tract also participates in many other regulatory metabolic,
and immunologic functions that affect the entire body.
. The Gastrointestinal tract:
The Ultimate Food Processor
Each day a varying mixture of foods enters the
gastrointestinal (GI) tract, and with remarkable
efficiency the GI tract goes about its tasks
1-Sight, aroma, even sounds and thoughts of food:
presence and nature of food in the mouth
2-Perception of hunger from the Gl tract; hypothalamus
signals after sampling substrates and hormones
3-Presence of food in the stomach
4-Presence of partly digested food and acid in the small
intestine .
All these factors lead to :
Start Gl hormone secretions and increase bile flow
and enzyme secretions from the stomach pancreas
and intestinal mucosa;
also increase G l motility ,blood flow, and growth .
Start GI Presence of digesta in the small intestine
and colon Slows gastric emptying, limits gastric acid
and enzymes secretion increases satiety, promotes
feeling of satiety Provides fuel for host and cells lining
GI tract, promotes growth of intestinal flora, promotes
satiety, slow supper G l motility stimulates defecation
The GI tract is also remarkable because of the following:
. The extent and type of hormonal, motor and secretory response
are appropriate for the amount and type of foods consumed.
. It is remarkably efficient in digestion and absorption of
foods and fluids, despite tremendous variations in types and
mixtures of foods. . It has the largest surface area, greatest
number of immune cells, and most hormones produced of all
organs.
It protects host tissues from strong acids and potent
digestive enzymes, a host of antigens, potentially toxic
compounds,
and high concentrations of microbes that coexist in the colon
just millimeters from sterile tissues
humans are considerably less efficient
at extracting energy from grasses,
stems, seeds, and other coarse fibrous
materials because they lack the
enzymes to hydrollze the chemical
bonds that link the molecules of sugars
that make up plant fibers. Fibrous foods
and any undigested carbohydrates are
fermented to varying degrees by
bacteria in the human colon,
Assignment
Hadeer kamal abo bakr
Recommended text book
Manual dietetic book