animal science ex 4 and 5

8/8/2019 Animal Science Ex 4 and 5

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Marjorie Pearl B. Alvarez

Animal Science 50 (Introduction to Animal Science)

Exercise No.4 Digestive System : Structure and Function

Introduction:

Digestion is the process by which food and other ingested material are broken down into (a)

nutrients that can be used by the body, and (b) waste products. Animals, for the most part,

ingest their food as large, complex molecules that must be broken down into smaller molecules

(monomers) that can then be distributed throughout the body of every cell. This vital function is

accpomplished by a series of specialized organs that comprise the digestive system. In simple

terms, the digestive system is a portal for nutrients to gain access to the circulatory system.

Foodstuffs are broken down to very simple molecules. Resulting sugars, amino acids, fatty acids,

etc. are then transported across the GI tract lining into blood.

The specific foodstuffs animals are able to utilize is dependent on the type of digestive system

they possess.There are many types of GI tracts in animals. Three types, non-ruminant, ruminant,

and avian are common in farm animals. These there different types are attributed to their

feeding habits.

Objectives:

At the end of the exercise, the students should be able to:

1. Able to distinguish different animals by their digestive system.2. Identify parts of the different digestive system of animals.3. Be able to familiarize the function of each part.4. Be able to discuss the processes of digestion relative to the type of digestive system.


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Pig digestive system

Region/organ Function

A. Pancreas

Produces the enzymes to digest proteins, fats and carbohydrates

in the small intestine.

Also produces the hormone insulin

B. Tongue Organ that mixes food in the mouth and makes swallowing happen


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C. Rumen Micro-organisms digest cellulose in this modified part of the stomach

D. Salivary glands Produce saliva containing salivary amylase

E. Oesophagus Carries the food from the mouth to the stomach

F. Gall bladder Stores bile

G. Pyloric sphincter This muscle controls the passage of food out of the stomach

H. Pharynx Both food and air pass along this

I.Rectum Indigestible matter held here before defecation

I. Liver Produces bile

J. StomachA bag made of muscle where food is held. Gastric juice and

hydrochloric acid are added here.

K. Small intestine

Where food is mixed with bile and digestion of proteins, fats and

carbohydrates takes place

L. Colon Water and salt are absorbed here

M. Functional caecum Where micro-organisms digest fibre in rabbits and horses


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Chicken digestive system

The alimentary canal

The alimentary canal is a long tube like organ starting at the beak at the head and ending with the vent

or cloaca in the abdominal region. Generally the alimentary canal has layers of muscle runninglengthwise and around it and is lined with mucous membranes. Glands producing important digestive

juices are found in different locations of the canal. The nutrients from the food, after digestion are

absorbed through the wall of the alimentary canal into the circulatory system for transport to the liver

or other parts of the body. The waste remaining is eliminated from the body via the cloaca or vent.

Mouth structure

In the fowl the lips and cheeks are replaced by the beak - an area of dense and horny skin lying over the

mandible and incisive bones that serve as the bony foundation. There are no teeth. The so called egg

tooth found on the end of the beak of newly hatched chickens is an aid to their escape from the egg at

hatching and disappears after a day or two. The hard palate, forming the roof of the mouth, presents along, narrow median slit that communicates with the nasal cavity (median - along the middle). The hard

palate has five transverse rows of backwardly pointing, hard, conical papillae. Numerous ducts of the

salivary glands pierce the hard palate to release their secretions into the mouth cavity.


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Salivary glands

A thick layer of stratified squamous epithelium covers the free surface. The salivary glands run the

whole length of the hard palate, the groups of glands merging to form one mass of glandular tissue

under the epithelium. Lymphoid tissue is found in most glands.

The salivary glands are:

1. Maxillary - in the roof of the mouth2. Palatine - on either side of the nasal opening in the roof of the mouth3. Apheno-pteryoid glands - in the roof of the pharynx on each side of the common opening for the

eustachian tubes (the eustachian tubes connect the middle ear to the mouth and their function

is to equalise the air pressure on each side of the tympanic membrane in the ear)

4. Anterior sub-mandible glands - in the angle formed by the union of the upper and lower beaksor mandibles

5. Posterior sub-mandibular glands6. Lingual glands - in the tongue7. Crico-arytenoid glands - around the glottis8. A small gland in the angle of the mouth

Pharaynx and tongue

The pharynx is continuous with or follows the mouth. The combined cavity of the mouth and the

pharynx is often referred to as the oropharynx. The common opening for the two eustachian tubes is

located in the middle of its dorsal wall (roof). The tongue is long and pointed and conforms to the shape

of the beak in which it operates. The epithelium of the tongue is thick and horny, especially towards the

tip. A transverse row of simple, large and horny papillae with their tips directed towards the rear of the

mouth cavity are located on the posterior end. The hyoid bone provides the framework to support the

tongue. The entoglossal bone extends longitudinally in the median plane. small patches of lymphatictissue are located throughout the corium. Mucous glands are located in the tongue with short ducts

directed towards the rear. Some but not others believe that there are taste buds located on the tongue.

In any case the sense of taste appears to be very weak if at all present.

The mouth has two major functions:

1. To pick up the food particles - this skill is modified by beak trimming. Birds with normal beaksbecome very adept at the manipulation of food particles thus leading to significant food

wastage and one effect of beak trimming is to reduce this wastage.

2. To direct the food into the oesophagus - as part of the birds eating behaviour.Oesophagus, crop and proventriculus

The oesophagus is wide and is capable of being significantly stretched. It connects the mouth region to

the crop in close assoc iation with the trachea. The crop is a large dilation of the oesophagus located just

prior to the oesophagus entering the thoracic cavity. The crop provides the capacity to hold food for

some time before further digestion commences. This capacity enables the bird to take its food as

meals at time intervals but permits continuous digestion. Inside the thoracic cavity, the oesophagus


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enters or becomes the proventriculus - a very glandular part of the digestive tract often called the

glandular stomach.

The wall of the oesophagus is composed of four layers of tissue the innermost being mucous membrane.

The mucous membrane is an important barrier to the entry of microbes and the mucous it produces is a

lubricant that aids the passage of the food along the alimentary canal. The structure below the crop is

similar to that above except there is less lymphoid tissue below the crop. The crop structure is similar to

that of the oesophagus except there are no glands present in fowls. Ducks and geese have glands in the

crop mucous membranes. In pigeons the surface cells of the crop slough off during brooding to form

pigeons milk - used to feed the baby pigeons in the nest.

Proventriculus

The glandular stomach or proventriculus is relatively small and tubular. The wall is very thick and is

composed of five layers:

1. Outer serous membrane.2. Muscle layer composed of three separate layers:

o Two thin longitudinal layers.o Thick circular layer.

3. Layer of areolar tissue containing blood and lymph vessels.4. Thick layer composed mainly of glandular tissue.5. Mucous membrane.

The glands form the greater part of the thickness of the organ. Simple single glands group to form

lobules each of which converges into a common cavity near the surface. The cavities converge to form a

common duct that leads to the surface through the apex of a small papilla (see Fig. 2). These glands

produce a number of juices or enzymes that are used in the digestion or breaking down of food into its

constituent nutrients (see Table 1). The mucous membrane is raised into folds and between these foldsare numerous simple tubular glands that produce hydrochloric acid as well as lymphoid tissue.

Gizzard

The muscular stomach or gizzard is located immediately succeeding the proventriculus. It is placed

partly between the lobes and partly behind the left lobe of the liver. It has a flattened, rounded shape

somewhat like a convex lens, with one side slightly larger than the other. Each surface is covered by a

glistening layer of tendinous tissue - thicker at the centre and becoming thinner towards the edges.

Under this outer layer very powerful masses of red muscle are located. The inner surface is lined with a

creamy coloured, thick, horny tissue raised in ridges. The gizzard almost always contains quantities of

hard objects such as gravel or other grit that aids in the disintegration of food - the primary function ofthe gizzard.

The entrance from the proventriculus and the exit to the duodenum are close together and dorsal in

location. The gizzard consists of a number of layers of tissues in some of which straight tubular glands

are located. The innermost layer is a strong, flexible skin able to withstand the potentially damaging

effects of the muscular action grinding the food often in the presence of stones or other insoluble


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material. The glands of the gizzard produce a liquid, keratinised material that passes to the surface of

the horny lining where it hardens to replace tissue worn away by the grinding action of the organ.

The small intestine

The small intestine begins at the exit from the gizzard and ends at the junction of the small intestine,caeca and colon. It is relatively long and has a constant diameter. Of the three parts of the mammalian

small intestine - the duodenum, jejunum and ileum, only the duodenum can be easily distinguished in

the fowl. There is no clear demarcation between the jejunum and ileum and the small intestine appears

as one long tube. Much of the digestion of the food and all of the absorption of the nutrients takes place

in the small intestine and hence its structure is quite important. The structure is as follows:

1. Serosa - a serous membrane on the outside of the intestine.2. A layer of longitudinal muscle - fibres run along the length of the intestine.3. A layer of circular muscle - three times as thick as the longitudinal muscle. Located between the

two muscle layers are:

o Blood vessels.o Lymph vessels.o A network of nerve fibres.

4. An ill-defined sub-mucosa - the areolar of the oesophagus.5. Mucous membrane consisting of:

o A thick muscularis mucosae of longitudinal and circular muscle.o Corium - many glands, lymphoid tissue, muscle fibres and a variety of free cells.o Epithelium or surface.

The small intestine has a number of very important functions:

1. Produces a number of enzymes involved in the digestion process2. Site of much of the digestion of the food3. Site of much of the absorption of food

Villi

When a piece of the small intestine is immersed in water it takes on a very velvety appearance because

of the presence of villi - long flattened, fingerlike projections extending into the lumen (inside) of the

intestine like flexible fingers. The villi are very actively involved in the absorption process. A single layer

of columnar epithelium together with goblet cells covers the lining. The goblet cells secrete mucous.

Permanent folds in the mucous membrane called the valves of kerkring are located at the proximal

end (closest to the front) of the duodenum.

A lacteal (lymph vessels), capillaries, bundles of plain muscle fibres, nerves and other tissues and cells

occupy the core of the villus. The villi have the function of providing a vastly increased surface area for

the more efficient absorption of the nutrients. The efficiency of the absorption is influenced by the

surface area available for the nutrients to move through - the more villi the better the absorption. They

also provide a means of concentrating the nutrients collection ability once they have moved through the

intestine wall.


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Duodenum

After the duodenum the small intestine forms a coil and is suspended from the dorsal wall of the

abdominal wall by a thin membrane - the mesentery. This membrane carries the blood vessels

associated with the intestine. The duodenum starts at the gizzard and forms an elongated loop about 20

centimetres long. The pancreas lies between the arms of the loop and being attached to each arm of theduodenum actually holds the two arms together.

Lymphoid tissue in the duodenum is very plentiful and is usually located in the corium. The lymphoid

tissue collects the lymph - the lymph vessels transport a special fluid other than blood that is found in

the spaces between cells and tissues till it passes into the blood system. Bile ducts from the gall bladder

attached to the liver and two to three pancreatic ducts enter the small intestine by a common papilla at

the caudal end (closest to the rear) of the duodenum. The pancreas, a very important organ in the

process of digesting food, is located closely associated with the duodenum being attached to each side

of the duodenal loop and lying between the two arms.

Jejunum and the ileum

The jejunum and the ileum, together about 120 cm long commence at the caudal end of the duodenum

where the bile and the pancreatic duct papilla is located and terminates at the ileo-caecal-colic junction.

This junction is where the small intestine, the two caeca and the colon all meet. This portion of the small

intestine is similar in structure to the duodenum except that:

1. It is suspended in the mesentery2. The villi are shorter3. There is less lymphoid tissue

Meckels Diverticulum is a constant feature about half way along the small intestine appearing as a small

projection on the outer surface of the small intestine. This projection is where the yolk sac was attached

during the development of the embryo.

Large intestine

The large intestine is very short and does not differ to any extent from the calibre of the small intestine.

It runs in nearly a straight line below the vertebrae and ends at the cloaca. Sometimes this section is

referred to as the colon and the rectum - the rectum being the terminal part. The bursa of fabricius is

located immediately above the cloaca of young birds but disappears when the birds have reached

approximately one year old.

Caeca

The two caeca or blind pouches are about 16-18 centimetres long in the adult. They extend along the

line of the small intestine towards the liver and are closely attached to the small intestine along their

length by the mesentery. Each caecum has three main parts:

1. A narrow base with thick walls arising at the ileo-colic-caecal junction2. Middle part with thin walls


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3. The wide blind apex with fairly thick wallsThe structure of the caeca is as follows:

1. Serous membrane2. Outer longitudinal muscle3. Circular muscle4. Inner longitudinal muscle forming the muscularis mucosae of the mucous membrane

The cloaca

Cloaca

The large intestine terminates in the front part of the cloaca. The cloaca is a tubular cavity opening to

the exterior of the body and is common to the digestive and urogenital tract. The structure of the cloacais very similar to that of the intestine except that the muscularis mucosa disappears near the vent. It

divides into three chambers, each separated by a constriction not readily defined:

1. The copradaeum - a continuation of the colon-rectum2. The urodaeum - middle part into which the ureters and genital ducts open3. The proctodaeum - opens to the exterior of the vent. Birds less than one year old have a dorsal

opening leading into the blind, rounded sac - the bursa of fabricius

Liver

The liver is a bi-lobed organ that lies ventrally (below) and posterior (in rear of) to the heart and isclosely associated with the proventriculus and the spleen. The right side lobe is the larger. The liver is

dark brown or chocolate in colour except for the first 10-14 days when it may be quite pale due to the

absorption of lipids (fats) from the yolk as an embryo. It weighs approximately 50 grams. The capsule or

glissosis, the membrane covering the organ, is thinner than that of mammals.


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The gall bladder lies on the right lobe beneath the spleen. Two bile ducts emerge from the right lobe.

One of these originates from the gall bladder and the second provides a direct connection from the liver

to the small intestine. A system of ducts connects the right and left lobes.

There are a number of functions that the liver carries out:

1. Bile formation - consisting of bile, various pigments and bile salts. Bile is involved in thedigestion of fats to fatty acids and glycerol

2. The metabolism of:o carbohydrate.o lipids.o protein.

3. Production and destruction of blood cells.4. Synthesis of plasma proteins and fibrinogen (associated with blood clotting).5. Storage of glycogen, fat and fat-soluble vitamins e.g. vitamin A.6. Detoxification of certain substances (detoxify - destroy the poisonous effect).

The liver cells have a high rate of destruction and a good regenerative capacity (re-growth ability).Notwithstanding this, in the normal animal, much of the organ is in reserve and can be removed or

destroyed without causing undue stress.

Ruminant

The stomach of ruminants has four compartments: the rumen, reticulum, omasum and abomasum, as

shown in the following diagram:

The ruminant stomachs, as seen from the right side

Collectively, these organs occupy almost 3/4ths of the abdominal cavity, filling virtually all of the leftside and extending significantly into the right. The reticulum lies against the diaphragm and is joined to

the rumen by a fold of tissue. The rumen, far and away the largest of the forestomaches, is itself

sacculated by muscular pillars into what are called the dorsal, ventral, caudodorsal and caudoventral

sacs. In many respects, the reticulum can be considered a "cranioventral sac" of the rumen; for example,

ingesta flows freely between these two organs. The reticulum is connected to the spherical omasum by

a short tunnel.


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The abomasum is the ruminant's true or glandular stomach. Histologically, it is very similar to the

stomach of monogastrics.

The interior of the rumen, reticulum and omasum is covered exclusively with stratified squamous

epithelium similar to what is observed in the esophagus. Each of these organs has a very distinctive

mucosa structure, although within each organ, some regional variation in morphology is observed.

Horse

The ForegutWhen your horse eats, her teeth grind and pulverize the feed. It travels down to her stomach, where it is

mixed, stored and partially digested before being passed to the small intestine or upper gut where most

nutrients are absorbed. Food passes through the stomach and small intestine quickly. If your horse eats

too much too quickly, large amounts of soluble carbohydrates may pass to the large intestine and

ferment, causing...you guessed it...colic.

The Hindgut

When the optimum amount of food passes through the small intestine, it enters the cecum (which

forms, with the large colon, the organ known as the large intestine or hindgut). The cecum ferments

undigested nutrients and passes the results on to the colon for further digestion. Fermentation

produces nutrients vital to your horse's health but fermentation can also produce a gas colic. If largeamounts of soluble carbs such as starch reach the hindgut, gases may be produced faster than your

horse can absorb or release them.

Duck digestive system


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1. Oesophagus includes enlarged area of crop.

2. Crop temporary storage and moistening of food, place for salivary amylase to work.

3. Proventriculus- corresponds to the true stomach, site for HCl and pepsin production.

4. Gizzard- muscular area which contains grit.

5. Pancreas

6. Duodenum-

7. Liver- The liver is a bi-lobed organ that lies ventrally (below) and posterior (in rear of) to the heart and

is closely associated with the proventriculus and the spleen8. Gallbladder

9. Ileum

10. Caecum

11. Cloaca

Differences:

Ruminants such as cattle and sheep, also have only one true gastric stomach but with additional

compartments which involved for fiber digestion. Non-ruminants include pig, horse, rabbit, dog and cat.

Humans also have a non-ruminant type of digestive tract. The avian GI tract is very different from the

non-ruminant and ruminant tracts.

Meanings:

Abomasum is considered to a very similar to the true gastric stomach which was described for non-

ruminant. In general the characteristics of the abomasums are identical to the gastric of the non-

ruminant. It is the fourth and final stomach compartment in ruminants and it secretes rennin.


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Amino Acid - the chemical units or "building blocks" of the body that make up proteins

Amylase - Amylase is an enzymeenzyme that helps digest carbohydrates. It is produced mainly in the

pancreas and the glands that make saliva. When the pancreas is diseased or inflamed, amylase releases

into the blood.

Bladder - Any pouch or other flexible enclosure that can hold liquids or gases but usually refers to the

hollow organ in the lower abdomen that stores urine.

Invertase - ) is an enzyme that catalyzes the hydrolysis (breakdown) of sucrose (table sugar).

Ruminant- with only one true gastric stomach, but with additional compartments which involved for

fiber digestion.

Rumination- can be described as controlled vomiting. In rumination, a controlled set of contractions of

the esophagus, reticulum, and rumen allow ingesta to be regurgitated back up to the esophagus where

fluids are swallowed again and additional re-mastication and re-swallowing of solid occurs.

Reticulum- used to move food into the rumen or omasum and collection of dense particles of food.

Cecum - ) is a pouch, connecting the ileum with the ascending colon of the large intestine.


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Marjorie Pearl B. Alvarez

Animal Science 50 (Introduction to Animal Science)

Exercise No. 5 Reproductive System: Structure and Function

Introduction

The role of reproduction is to provide for the continued existence of a species; it is the process by which

living organisms duplicate themselves. Animals compete with other individuals in the environment to

maintain themselves for a period of time sufficient to enable them to produce tissue nonessential to

their own survival, but indispensable to the maintenance of the species. The additional tissue,

reproductive tissue, usually becomes separated from the individual to form a new, independent

organism. Reproductive system of animals vary on the size and shape among different species.

Objectives:

At the end of the exercise, students are expected to:

1. Locate the parts of the reproductive systems of farm animals both male and female.2. Identify the specific function of each part and discuss the hormonal interplays in male and

female reproduction.


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Male Reproductive System


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Female Reproductive System

Ovaries principal sex organs which have two functions: a.production of sex cell (ovum) and b.

production of female sex hormone (estrogen).

Oviduct- is a tubular structure connecting the infundibulum to the horn of the uterus.

Cervix- sometimes considered as the neck of the uterus.

Vagina- primary organ of copulation.

Vulva- common passageway for the products of reproduction and for urine.

Definitions:

Estrus - the periodic sexual excitement of most female placental mammals; the period of this when the

female will accept mating with the male, characterized by changes in the sex organs


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Lactation - Secretion or formation of milk by the mammary glands. The period during which the

mammary glands secrete milk.

Gestation - The period of development in the uterus from conception until birth

Fertilization- The act or process of initiating biological reproduction by insemination

Parturition is define as the physiological process by which the pregnant uterus delivers the fetus and

placenta from the maternal organism.

Farrowing - To give birth to (a litter of pigs)

Calving - the process of giving birth to a calf

animal science ex 4 and 5

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