Describe Anatomy and Physiology of Horses

Equine Science

For sixty seconds, write down every body function you are currently

using, some without thinking about it.For example, you are breathing—that would be respiratory system.

Just like you have systems in your body to ensure

proper health, so does the horse.

There are many systems to study. Today we will introduce each major system in the

horse.

Objectives

Today we will:Describe the digestive systemDescribe the skeletal systemDescribe the muscular systemDescribe the reproductive systemDescribe the nervous systemDescribe the circulatory systemDescribe the respiratory system

The Digestive System The digestive system is responsible for the

breakdown and absorption of nutrients. Its parts, in order from front to back, are

called the mouth, pharynx, esophagus, stomach, small intestine, cecum, large colon, small colon and rectum.

The alimentary canal is roughly 100 feet long in an average horse, but the stomach is relatively small, holding 3-4 gallons when full. This is one reason it is better to feed horses small quantities at frequent intervals.

Digestive System

http://www.google.com/imgres?imgurl=http://3.bp.blogspot.com/-uydvXqvEUQ8/TZyuoaTa0QI/AAAAAAAAASw/qCN2mJh0yi0/s1600/digestive_system.jpg&imgrefurl=https://www.pinterest.com/lmalyk/horse-work-sheets/&h=300&w=450&tbnid=3gw3kHOY3YtGjM:&zoom=1&docid=uxIkxa_QYdBQ1M&ei=vHtzVZL2IdLYoAShuoCYAQ&tbm=isch&ved=0CC4QMygSMBI

The Skeletal System Horses are members of phylum Chordata, sub-

phylum Vertebrata. They have an internal skeleton which include a backbone.

The horse's "backbone" stretches along the topline from the poll in front into the tail in the rear, and is not actually a single bone, but linked vertebrae.

The horse's skeleton as a whole supports the horse's body, defines the basic shape or framework, protects delicate internal organs and provides attachment points for the muscles that make movement possible.

It also houses the bone marrow, which is where blood cells form. Ligaments help connect bones.

Skeletal System

http://www.thinklikeahorse.org/images/horseanatomy.png

The Muscular System Muscles attach to the skeleton (by way of tendons),

and do the work of moving parts of the animal. Muscles can work only by contracting, pulling - they

cannot push. Therefore, many muscles are in pairs - one to extend (or straighten) a joint, and the other to flex (or bend) that joint.

There are three main types of muscle - skeletal muscle, which is what we usually think of when we think 'muscle', and which helps the horse walk, trot, gallop, eat, or look around; smooth, or involuntary, muscle, like the muscles of the digestive system which push the food through the alimentary canal; and heart muscle.

The Muscular System (continued)

The skeletal muscle fibers may be classed as two kinds: slow twitch and fast twitch.

Draft horses and sprinters tend to have more 'fast twitch' muscle fibers, which are more powerful in the short term.

Endurance horses and stayers tend to have more 'slow twitch' muscle fibers, which can work longer.

In order to work efficiently, muscles must be able to relax between contractions - a muscle that is constantly contracting without frequent, short breaks to relax will become tired, stiff, and more prone to injury.

Muscles generally get stronger with work, but overworked muscles will not be able to repair minor damage quickly enough, and may be torn, or strained.

The Muscular System (continued)

In the living body, different muscles are layered over each other, often two, three or four layers deep.

Therefore, it takes more than a single picture to show many muscles.

The next two diagrams do not show how the muscles look, but only their locations relative to the skeleton, and include many, but by no means all, of the equine muscles.

Muscular System-Group 1

https://share.ehs.uen.org/node/1570

Muscular System-Group 2

https://share.ehs.uen.org/node/1570

The Reproductive System Horses have a typical mammalian reproductive

system. A stallion has testicles and a penis, which is usually

protected inside the sheath. A mare has ovaries, a uterus and vagina. During the breeding season (from early spring till early

autumn) the mare becomes fertile at roughly three-week intervals.

The several days when she will accept the stallion, she is said to be "in heat" or “in season” for breeding.

Reproductive Systems

http://www.google.com/imgres?imgurl=http://www.merckvetmanual.com/media/pet/figures/DDH_mare_reproductive_system.gif&imgrefurl=http://www.merckvetmanual.com/pethealth/horse_disorders_and_diseases/reproductive_disorders_of_horses/the_gonads_and_genital_tract_of_horses.html&h=412&w=450&tbnid=6n_3-Cv2cFVHJM:&zoom=1&docid=P4VLX3zxr72mlM&ei=0HdzVaf7HpfioASUlrfwDA&tbm=isch&ved=0CBwQMygAMAA

http://www.google.com/imgres?imgurl=http://www.merckvetmanual.com/media/pet/figures/DDH_stallion_reproductive_system.gif&imgrefurl=http://www.merckvetmanual.com/pethealth/horse_disorders_and_diseases/reproductive_disorders_of_horses/the_gonads_and_genital_tract_of_horses.html&h=637&w=450&tbnid=BLfDZ4jjyAyGPM:&zoom=1&docid=P4VLX3zxr72mlM&ei=0HdzVaf7HpfioASUlrfwDA&tbm=isch&ved=0CB4QMygCMAI

The Nervous System The nervous system consists of the central nervous

system (the brain and spinal cord), and the peripheral nervous system (the nerves in the rest of the body).

Through the nerves to the sensory organs (ears, eyes, nose, tongue and skin), the horse perceives information about what is going on around him.

Through the nerves to all the organs and systems of the body, the horse's brain coordinates all activities, including breathing, heartbeat, movement, and digestion.

You might consider the nervous system to be the communications and control department for the body.

Nervous System

http://www.merckvetmanual.com/media/pet/figures/DDH_horse_nervous_system.gif

The Circulatory System

As do all mammals, horses possess a four-chambered heart which receives blood from the veins, and pumps it out into the arteries to keep the entire body supplied with oxygen and nutrients, and to move out waste products like carbon dioxide.

Along with the heart and blood vessels, the circulatory system includes the blood, the lymph nodes and vessels, and lymph.

The lymph system is part of the immune defenses which protect the horse from disease.

Circulatory System

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http%3A%2F%2Fwww.gutenberg.org%2Ffiles%2F23403%2F23403-h%2F23403-h.htm&ei=XXlzVbeVNsTEsAX7voF4&psig=AFQjCNHcf2CZv1j-L6wvQJlnjY03RXFwVA&ust=1433717417799709

Circulatory System—Heart

http://www.google.com/imgres?imgurl=http://www.vetgo.com/cardio/concepts/images/heart_labelled_large2.jpg&imgrefurl=http://www.vetgo.com/cardio/concepts/concsect.php?sectionkey%3D9&h=347&w=346&tbnid=LejoCPiAB3M7EM:&zoom=1&docid=ITyrw76AX2xqEM&ei=RJN0Vc2WLIa4ogSIvpdI&tbm=isch&ved=0CB8QMygDMAM

Respiratory System

The respiratory system is the breathing apparatus - nostrils, larynx, trachea and lungs.

Unlike humans, horses cannot easily breath through their mouths, but must move all air in and out through their nostrils.

Like humans, the horse's respiratory system is vulnerable to colds, coughs, pneumonia and even "emphysema" (Chronic Obstructive Respiratory Disease - often called heaves in horses).

Horses must often live in dusty environments, and eat dusty hay, stressing their lungs. As athletes, horses need healthy lungs to perform well.

Respiratory System

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http%3A%2F%2Ffhotd64476.yuku.com%2Ftopic%2F49913%2FPics-of-Throat-Conformation&ei=Wpp0VeORAYrJtQXopoHoBg&psig=AFQjCNE0YrWgj5OtUaTWfUWOQy2dnfBSbQ&ust=1433791433268204

Systems Activity

Pick three of the systems we discussed

Draw and label a picture of each system and its components

For each system describe why it is important to the horse

Post your pictures around the classroom

Questions for Review

Which system is responsible for supporting the body?

Which system is responsible for moving parts of the body?

Which system is responsible for breathing?

Which system is responsible for oxygenating blood?

Which system is responsible for absorbing nutrients from food?

Questions for Review

Which system is responsible for supporting the body? Skeletal System

Which system is responsible for moving parts of the body? Muscular System

Which system is responsible for breathing? Respiratory System

Which system is responsible for oxygenating blood? Circulatory System

Which system is responsible for absorbing nutrients from food? Digestive System

Summary

Just like in humans, the equine body is formed by many systems working together to ensure health of the animal

Though we covered several systems, there are others we did not have time to discuss like the excretory, endocrine, immune, and integumentary system.

In order to fully understand the anatomy and physiology of the horse, we need a basic understanding of the primary systems.

If you want to learn more, there are many resources available online that can help you—we can even dissect a horse fetus to further study these systems.

References

The Merck Veterinary Manual: https://www.merckvetmanual.com/mvm/index.html

Overview of Equine Body Systems: https://share.ehs.uen.org/node/1570

Equine Colic Surgery: https://www.youtube.com/watch?v=mfysbxvqb40

Texas College and Career Readiness Standards

English Language Arts: V. Research, B, 1, a-b Science: VI: Biology, E. 1, F. 1-2 Social Studies: IV. Analysis, Synthesis, and

Evaluation of Information. B, 2-4; V. Effective Communication. A. 1-2.

Developed by the Department of Agricultural Leadership, Education & Communications,

Texas A&M Universityfor the Texas Education Agency, Educational Excellence Project for

AFNR©Texas Education Agency, 2015