Transcript Principals of General Zoology (Zoo-103)

Lecture 22: Animal physiology
Nutrition ‫التغذية‬
 Nutrition (nourishment) is the need of cells and organisms of
the materials (in the form of food) necessary for life.
 Nutriton is a process of intake of nutrients ‫( المواد الغذائية‬like
carbohydrates, fats, proteins,vitamins, minerals and water) by
the organism and the utilisation of these nutrients by the
organism.
 The diet ‫ الوجبة‬of an organism is what it eats.
 A poor diet can have a negative impact on health, causing
deficiency diseases such as scurvy ‫اإلسقربوط‬, beriberi, healththreatening conditions like metabolic syndrome ‫مشاكل أيضية‬.
Nutrients ‫املواد الغذائية‬
 There are seven major classes of nutrients:
carbohydrates, fats, fiber, minerals, protein, vitamin,
and water.
 They are classified into two kategories:
I)- Macronutrients ‫مغذيات كبيرة‬: needed in relatively large
amounts. They are carbohydrates, fats, fibers ‫ألياف‬,
proteins, and water.
II)- Micronutrients ‫مغذيات صغيرة‬: needed in smaller
quantities. They are minerals ‫ األمالح المعدنية‬and vitamins .
 The macronutrients (but not fibers and water) provide structural
material ‫ مواد بنائية‬for example (amino acids from which proteins are
built) and (lipids from which cell membrane is built).
 Some of the structural materials can be used to generate energy
internally ‫لتوليد الطاقة داخليا‬, and measured in kilocalories ‫( كيلو كالوري‬often
called "Calories").
I- Carbohydrates and proteins provide 4 kcal of energy per gram.
II- while fats provide 9 kcal per gram.
 Vitamins, minerals, and water do not provide energy, but are
required for other reasons.
 Fibers (i.e., non-digestible materials such as cellulose), seems to be
required, for both mechanical and biochemical reasons.
 Fats are triglycerides, made of fatty acid monomers bound to
glycerol backbone. Some fatty acids, but not all, are essential in
the diet: they cannot be synthesized in the body.
 Protein molecules contain amino acids, some of which are
essential (the body can not make them internally). Some of the
amino acids are convertible to glucose and can be used for energy
production just as ordinary glucose during prolonged starvation.
 Most foods contain a mix of some or all of the nutrient classes,
together with other substances such as toxins or various sorts.
 Some nutrients can be stored internally (eg, some vitamins),
while others are required more or less continuously.
 Poor health results from a lack of required nutrients or, too
much of a required nutrient. For example, both salt and water
(both are required) but cause illness (or even death) in too large
amounts.
Digestion‫اهلضم‬
 Digestion: is the mechanical and chemical breaking
down ‫ تكسير‬of food into smaller components, to a form
that can be absorbed ‫تُمتص‬.
 Digestion is a form of catabolism that means break
down of macro-food molecules ‫ أجزاء الطعام الكبيرة‬to smaller
one.
a)- Extracellular digestion ‫الهضم خارج الخلية‬: In mammals, food enters the mouth,
being chewed by teeth, and broken down by the saliva ‫ اللعاب‬from the salivary
glands. Then it travels down the esophagus ‫ البلعوم‬into the stomach ‫المعدة‬, where
acid begins physical break down of some food. The food go through the small
intestine ‫األمعاء الدقيقة‬, through the large intestine ‫األمعاء الغليظة‬, and are excreted
outside.
b)- Intracellular digestion ‫الهضم داخل الخلية‬: Some other unicellular organisms ‫الكائنات‬
‫ وحيدة الخلية‬use different mechanisms to digest food inside the cell.
Digestive systems ‫اجلهاز اهلضمي‬
 Once food is inside the organism, digestion can be conducted in
the cytoplasm, in a vesicle , through a tube, or through
specialized organs aimed at making the absorption of nutrients
more efficient.
 Diggestive systems are classified into two kategories:
a -)Gastrovascular cavity :‫ التجويف الوعائي المعوي‬functions as a stomach in
both digestion and the distribution of nutrients to all parts of the body.
Digestion takes place within this central cavity ‫ التجويف المركزي‬which has
only one opening to the outside that functions as both a mouth ‫ فم‬and an
anus ‫ شرج‬. So, it is described as an incomplete gut ‫معي غير كامل‬.
b)- Complete gut : ‫المعي الكامل‬has specialized organs ‫ أعضاء متخصصة‬that aid
in the digestion of their food. Here, animals were created with organs
such as beaks ‫مناقير‬, tongues ‫ألسنة‬, teeth ‫أسنان‬, a crop ‫حوصلة‬, gizzard ‫القانصة‬,
and others.
1. Beaks: birds eat primarily seeds, nuts, and fruit, using their beaks to open even the
toughest seed ‫البذور الجافة‬.
2. Tongue: is skeletal muscle on the floor of the mouth that manipulates food for
chewing (‫ )المضغ‬and swallowing (‫)البلع‬. The underside of the tongue is covered with a
smooth mucous membrane ‫ غشاء مخاطي‬. The tongue is utilized ‫ يوظف‬to transport food
down to the esophagus.
3. Teeth: (singular, tooth) are small whitish structures found in the jaws (‫ )الفكوك‬of
many vertebrates that are used to chew food ‫مضغ الطعام‬. They are not made of bone,
but rather of tissues of varying density and hardness.
- Teeth of carnivores ‫ آكالت اللحوم‬are shaped to kill and tear meat ‫وتمزق اللحم‬.
- Teeth of herbivores ‫ آكالت العشب‬are made for grinding ‫ طحن‬plant parts.
4.
Crop: is a thin-walled expanded portion ‫ جزء واسع رفيع الجدار‬of the
alimentary canal used for the storage of food prior to digestion ‫تخزين‬
‫الطعام قبل الهضم‬. In some birds it is an expanded, muscular pouch ‫ كيس‬near
throat ‫قرب الزور‬. In adult pigeons, the crop can produce crop milk ‫لبن‬
‫الحوصلة‬to feed newly hatched birds.
Certain insects may have a crop or enlarged oesophagus.
5.
Gizzard: is a specialized stomach with thick ‫سميك‬, muscular walls used
for grinding up food ‫طحن الطعام‬.
Birds and cockroaches have developed gizzards to assist in the digestion of
tough materials. The gizzard can grind food with stones that have been
swallowed and pass it back to the true stomach and vice versa.
6. Abomasum ‫المعدة الحقيقية‬
Herbivores have evolved cecums (or an abomasum in the case of
ruminants ‫)الحيوانات المجترة‬. Ruminants have a fore-stomach ‫ معدة أمامية‬with
four chambers. These are the rumen ‫ الكرش‬, reticulum ‫ الشبكية‬, omasum
‫الورقية‬, and abomasum)‫ األنفحة (المعدة الحقيقية‬:
 In the first two chambers (the rumen & the reticulum) the food is mixed with
saliva and separates into solid and liquid materials. The solid is then
regurgitated ‫يُسترجع‬, chewed slowly ‫ يمضغ ببطء‬to completely mix it with saliva
and to break down the particle size.
 In the 3rd chamber (omasum) water and many of the inorganic mineral
elements are absorbed into the blood stream.
 The 4th chamber (abomasum) which is equivalent of the human stomach. It
serves primarily as a site for digestion of microbial and dietary protein. Digesta
is finally moved into the small intestine for absorption of nutrients.