Figure 2.5: Internal Structure of the Ruminant’s Digestive System  
DIGESTION IN A RUMINANT  
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The digestion  
process  
in ruminants  
starts  
in the mouth when plant  
materials are partially chewed by teeth.  
The partially chewed food is mixed with saliva and then rolled into a bolus  
by the tongue. The rolled food is then swallowed through the oesophagus.  
The swallowed food enters the rumen where is it temporarily stored. Rumen  
is very large; therefore, it can store large amount of food at a time. In the  
rumen, there are bacteria that act upon the swallowed food and digest  
cellulose contained.  
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When the animal is resting, the food stored in the rumen is brought back  
to the mouth (regurgitated) periodically for further chewing. The chewed  
food is mixed with saliva, rolled and swallowed again.  
Instead of the food passing again into the rumen, it passes to the second  
chamber of the stomach called the reticulum where the food is mixed  
thoroughly with water and becomes soft, watery and less greenish.  
Form the reticulum, the food passes to the third chamber of the stomach  
called omasum where the food is further mixed and some water is absorbed  
from it. In this chamber, the food is in fine particles and less watery.  
Then, the food proceeds into the fourth chamber of the stomach called  
abomasum. The abomasum secretes gastric juice that contains hydrochloric  
acid and digestive enzymes. The hydrochloric acid kills the bacteria which  
come with the food material. The digestive juices contain enzymes that  
digest carbohydrates, cellulose, proteins and fats.  
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From this point, the digestion process continues as in human beings.  
Table 2.2: Differences Between the Digestive System of Human Beings and That  
of Ruminants.  
S/N  
Ruminants  
Human beings  
(i)  
Their stomach is divided into four  
chambers called rumen, reticulum,  
omasum and abomasum.  
They have only one stomach.  
(ii)  
They  
can  
regurgitate  
food (bring  
They cannot regurgitate (bring food  
back to the mouth).  
food back to the  
swallowed food.  
mouth), rechew  
(iii)  
(iv)  
They  
have  
bacteria  
that  
breaks  
They do not have bacteria that can  
break down cellulose or fibres.  
The cellulase enzyme is absent in  
their digestive system, hence there  
is no cellulose digestion.  
down cellulose of fibres.  
They have cellulase enzyme in their  
digestive system which is involved  
in cellulose digestion.  
(v)  
They have a type of teeth called  
horny pad for chewing food instead  
of upper incisors and canines.  
They have teeth such  
as upper  
incisors and canines for chewing  
food.  
EXERCISE  
1. Describe features that allow cows and goats to be classified as ruminants.  
2. How can you differentiate the stomach of the cow from that of human being?  
3. Human beings cannot eat grasses whereas cows can. Support the statement.  
4. Explain the adaptive features of the ruminants’ digestive system.  
HUMAN DIGESTIVE SYSTEM DISORDERS AND DISEASES  
(a) Dental Caries. This is commonly referred to as tooth decay. When there is food  
remains in the mouth, bacteria present in the mouth combine with saliva and with  
the food remains to form plaque.  
NOTE: Plaque is the sticky substance often found between teeth. Bacteria in a plaque  
convert food remains especially starch and sugar into lactic acid. The acid dissolves  
the tooth enamel forming a hole in it.  
Causes of Dental Caries  
Too much sweet food. Sweet food tends to encourage growth of bacteria.  
Deficiency of calcium in the diet.  
(i)  
(ii)  
(iii) Deficiency of vitamin D.  
(iv) Lack of proper teeth cleaning which encourages food accumulation.  
Symptoms of Dental Caries  
(i)  
Toothache, especially after eating sweet, cold or hot foods.  
Gums bleeding especially during tooth brushing.  
(ii)  
(iii) Development of holes or cavities in the teeth.  
Prevention and control of Dental Caries  
Brush teeth regularly with recommended toothpaste at least twice a day to  
(i)  
remove plaque.  
(ii)  
Use dental floss when necessary to remove the plaque between your teeth.  
(iii) Wash your mouth after taking sugary foods like cakes, chocolates and biscuits.  
(iv) Minimize intake of sugary foods. This helps to limit the amount of acid produced  
by bacteria.  
(v)  
Avoid taking very hot or very cold drinks or foods  
(vi) Visit a dental clinic regularly for dental check-ups.  
(vii) Eating diet rich in calcium minerals.  
(b) Heartburn: This is a condition that results from extensive production o f  
hydrochloric acid. This hydrochloric acid (HCl) causes a burning or painful  
sensation  
in the  
oesophagus.  
The stomach  
contents  
flow  
back to  
the  
oesophagus because the cardiac sphincter is not closed properly.  
Causes of Heartburn  
(i)  
Secretion of excess hydrochloric acid in the stomach.  
(ii)  
Eating foods rich in acids in nature. For example; pepper, citrus fruits, fatty  
foods, chocolate, spicy foods and carbonated drinks such as soda.  
(iii) Taking in very hot or very cold foods.  
(iv) Taking in drugs such as alcohol, caffeine, (from tea, coffee or cola), cocaine and  
tobacco.  
(v)  
Lying down or bending over soon after eating.  
(vi) Pressure on the stomach due to pregnancy, obesity, tight clothing or vigorous  
body exercises.  
Symptoms of Heartburn  
A burning or irritating sensation in the chest or throat.  
A sour taste in the mouth.  
(i)  
(ii)  
(iii) Excessive belching, (i.e. to let air come up noisily from the stomach and out  
through the mouth).  
(iv) Difficulty swallowing.  
(v)  
Hoarseness or loss of voice.  
Prevention and Control Treatment of Heartburn  
(i)  
Minimize intake of foods that can cause heartburn such as pepper, citrus fruits,  
too much fatty, or too much sugary foods like sweets.  
Avoid alcohol, caffeine, (from tea, coffee or cola), cocaine and tobacco and  
recreational drugs.  
(ii)  
(iii) Avoid obesity and reduced body weight if you are obese.  
(iv) Avoid eating very hot or very cold foods.  
(v)  
Do not eat a large amount of food just before going to bed.  
(vi) Avoid late-night meals or engaging in vigorous body exercise immediately after  
eating food.  
(vii) Avoid wearing tight clothes that put pressure on the stomach.  
(viii) Use a wedge-shaped pillow to raise your head while sleeping.  
(ix) Taking measures to reduce stress.  
(x)  
Drinking enough water to dilute the acid in the stomach.  
(xi) Change diet of you have a history of being affected by certain types of food.  
(xii) Taking antacid tablets or alkaline substances which neutralize the acid of the  
chyme. It may include, sodium bicarbonate (baking powder) and domestic ashes.  
(c) Indigestion: In this condition, the food is not properly digested or digestion  
takes place very slowly. The affected person lacks appetite and feels full most  
of the time.  
The causes of indigestion  
(i)  
Inadequate enzyme secretion  
(ii)  
Working under very high pressure leading to stress.  
(iii) Food poisoning  
(iv) Sickness such as ulcers in the stomach or duodenum.  
(v)  
Eating too much spicy food or fatty food.  
(vi) Taking meals very late nights before going to bed.  
(vii) Swallowing to quickly without proper chewing.  
(viii) Eating too much food.  
Symptoms of Indigestion  
(i)  
Tendency of feeling full for long time, even 2-3 days.  
Lack of appetite.  
(ii)  
(iii) Stomach discomfort and restlessness.  
(iv) Nausea and vomiting.  
Prevention and control of Indigestion  
Set and adhere to meals timetable.  
Avoid too spicy and too fatty foods.  
(i)  
(ii)  
(iii) Avoid stress and maintain sensible life.  
(iv) Ensure good work management.  
(v)  
Eat balanced diet.  
(vi) Time for taking meals should be planned properly so that there is enough time  
for each meal to be eaten in a relaxed way.  
(vii) Seek medical advice for a prolonged indigestion problem.  
(viii) Exercise to help food digestion.  
(d) Constipation: This is a condition involving an experience of difficulty during  
defecation. It occurs when stool becomes hard and dry due to excessive  
absorption of water in the colon.  
Causes of Constipation  
(i)  
Extensive absorption of water in the colon.  
Lack of roughages or fibres in a meal.  
(ii)  
(iii) Low intake of liquids including drinking enough water.  
(iv) Over-reliance on dry foods such as bread. If such foods are taken  
without enough water, will result in constipation.  
(v)  
Presence  
of infectious  
agents like bacteria  
or worms which affect  
rhythmic movement of food, i.e. slowing the food movement leading to  
extensive water absorption in the colon hence constipation.  
(vi) Ignoring the urge for a long call.  
(e) Ulcers: These are sores or broken parts of the digestive system. There are  
two types, depending on the region of the gut;  
(i) Peptic ulcers; are ulcers of the stomach wall.  
(ii) Duodenal ulcers; are ulcers of the duodenal wall.  
Causes of Ulcers  
(i)  
Excessive secretion of acid and pepsin by gastric mucosa.  
(ii)  
Bacteria called Helicobacter pylori, which break down the gastric and  
duodenal mucosal barrier and expose it to digestive enzyme an d HCl.  
(iii) Smoking also causes ulcer development. Smoking increases ner vous  
stimulation of the stomach secretion glands, hence excessive HCl  
excretion.  
(iv) Stress contributes to ulcer formation. Since stress increases HCl acid  
secretion, hence increases the chance of mucosal barrier to erode.  
Thinking also increases production of HCl.  
(v)  
Alcohol causes ulcers. Alcohol breaks down the mucosal barrier,  
exposing it to HCl acid.  
(vi) Keeping the stomach empty for a long time can cause ulcers.  
(vii) Use antibiotics to kill infectious bacteria that cause ulcers.  
Symptoms of Ulcers  
(i)  
Burning pain in the stomach or in the middle of the thorax.  
Tiredness and weakness.  
(ii)  
(iii) Nausea and vomiting.  
(iv) Blood drops in vomit or stool (a sign of bleeding ulcers)  
(v)  
Heartburn  
Prevention and control of Ulcers  
(i)  
Avoid keeping the stomach empty for a long time.  
(ii)  
Avoid acid-producing foods like starch-rich food, pepper, citrus fruits.  
(iii) Avoid smoking, taking alcohol, aspirin and caffeine.  
(iv) Avoid emotional stress, and overthinking.  
(v)  
Adhere to personal and food hygiene to avoid infections.  
(f) Flatulence (Burping): This is a condition of releasing gas from the digestive  
system (form the colon) through the anus. The gases are odorless, but they  
come out with an unpleasant smell. One of these gases is hydrogen sulfide,  
and they are produced by the action of bacteria on the food in the large  
intestine.  
Causes of Flatulence  
(i)  
Unconscious swallowing of air during eating.  
Eating foods that produce gas such as cabbages, beans, boiled eggs,  
onions, garlic, milk and bread.  
(ii)  
(iii) Eating meals that have too much fat leading to the production of large amounts  
of carbondioxide gas.  
(iv) Poor absorption of carbohydrates in the gut.  
(v)  
(vi) Taking in aerated food such as soda.  
Symptoms of flatulence  
Smoking.  
(i)  
Abdominal pain.  
(ii)  
(iii)  
(iv)  
Constant urge to pass out gas through the anus.  
Excessive belching.  
Bloating (an accumulation of gas in the stomach).  
Prevention and control of Flatulence  
(i)  
Avoid foods that produce gas or eat them in moderate amounts.  
Those who are intolerant to lactose should avoid drinking or eating  
milk products.  
(ii)  
(iii)  
Avoid lying down just after eating because it makes it easy for gas to  
pass from the stomach into the intestines.  
(iv)  
(v)  
Chew food thoroughly to assist proper digestion of carbohydrates.  
Avoid eating foods containing too much fats or sugar.  
Cover the mouth during yawning to avoid swallowing of air.  
Minimize intake of aerated drinks.  
(vi)  
(vii)