Horse Anatomy PDF

Under the Horses Skin www.equestricare.com.au [email protected] 1300 378 768  The Skeleton "The framework around which soft tissues are attached" The skeleton is the framework for the horse’s body. It gives the muscles a scaffold to...

Under the Horses Skin www.equestricare.com.au [email protected] 1300 378 768  The Skeleton "The framework around which soft tissues are attached" The skeleton is the framework for the horse’s body. It gives the muscles a scaffold to attach on to and defines the horse’s size and shape.It is made up of bones supported by ligaments. These bones function to: Support the body Protect the vital organs such as the lung and heart Provide somewhere for the skeletal muscle to attach Store minerals such as Calcium (Ca), Phosphorous (P), Magnesium (Mg), Sodium (Na) and Potassium (K) which make up 70% of bone. Store organic collagen which makes up 30% of the bone. Produce red blood cells through bone marrow. You might be interested to know that bone is not set and continually remodels itself with increasing and decreasing amounts of stress, diet and blood supply. Increasing work can cause the bone to lay down more layers (ie. Roadwork) and things such as mineral deficiency can cause a decrease in bone. Bones can be classified as dense or spongy. They can be: Long: ie. Humerus, femur and tibia which act as levers. Short: ie. Carpus (knee) and tarsus (hock) bones which act as shock absorbers. Flat: ie skull bones and rib bones which protect vital organs. Irregular: ie. Vertebral bones which provide flexion. The surface of the bone is covered with a tough membrane (periosteum) that forms a protective skin, and between the bones is cartilage which reduces friction and concussion. www.equestricare.com.au Components of the skeleton Horses have approximately 205 bones. These can be divided into: 1. Axial Skeleton Skull 34 Bones Vertebrae 54-61 Bones Ribs 36 Bones (18 pairs) Sternum 1 Bone 2. Appendicular Skeleton Thoracic Limbs 40 Bones Pelvic Limbs 40 Bones www.equestricare.com.au  Axial Skeleton Skull The skull is made up of 34 bones and four cavities: 1. Cranial cavity – protects the brain 2. Orbital cavity – surrounds and protects the eye 3. Oral cavity – passage into the respiratory and digestive systems 4. Nasal cavity – leads into the respiratory system. www.equestricare.com.au  Axial Skeleton Vertebrae & Ribs The most important aspect of the horses skeleton in relation to the muscles is the vertebrae. The vertebrae can be divided into 5 sections as below. The vertebral formula is “C7-T18-L6-S5-Ca15-21” which is named for the number of vertebrae in each section. The ribs attach onto each thoracic vertebrae Notes: Notable vertebrae include the 1st (atlas/C1) and 2nd (axis/C2) cervical vertebrae. Some horses may have an extra 19th pair of ribs. The 5 sacral vertebrae are fused together to form the sacrum. Some Arabian horses have one less lumbar vertebrae. The withers are made up of the dorsal spinous processes of thoracic vertebrae 5-9. Sternum The sternum of the horse is attached to the ribs via ligaments. It consists of multiple sternebrae which fuse to form the one bone of the sternum. www.equestricare.com.au  Appendicular Skeleton Thoracic Limb The thoracic limbs of the horse are the front legs. They attach to the axial skeleton via muscles and tendons. The bones of the thoracic limb consist of the: Scapula, humerus, radius, carpus (8 carpal bones), cannon, splints, long pastern, short pastern, pedal bone. www.equestricare.com.au  Appendicular Skeleton Pelvic Limb The pelvic limbs of the horse are the hind legs and attach to the axial skeleton via the pelvis. The bones of the pelvic limb are the: Pelvis (Sacrum, Ilium & Ischium), femur, tibia, fibula, tarsus (7 tarsal bones), cannon, splints, long pastern, short pastern, pedal bone. www.equestricare.com.au  The Skeleton Bony Landmarks The bony landmarks are the areas of skeleton you can see through the skin and muscle. www.equestricare.com.au  Joints Joints, in general, link bones together. A joint is composed of two bones sitting in a joint cavity, connected to each other by a ligament. Each bone is protected on the end by cartilage, and the joint cavity is filled with synovial fluid to act as lubrication. Joints can be moveable, semi-moveable or fixed. Note: When you think of a joint you ultimately think of knee’s, hocks, fetlocks etc.. but did you know that there is a joint between each vertebrae? Types of Joint: Moveable 1. Ball and Socket: Allows whole movement, forward/back and side to side. ie. Shoulder and hip 2. Hinge Joint: Allows movement on one plane. ie. Elbow joint 3. Plane Joint: Allows sliding movement. ie. Knee joint 4. Condylar Joint: Allows flexion and extension with some rotation. Ie. Stifle 5. Pivot Joint: Allows rotation on the longitudinal axis. ie. Poll and first two vertebrae 6. Saddle Joint: Allows movement in only two planes. ie. Pastern joint. Types of Joint: Semi-Moveable Flex but do not moves as such. ie. Between vertebrae Types of Joint: Fixed Do not move at all. ie. Skull, sacrum & croup www.equestricare.com.au  The Soft Tissues Tendons Tendons are part of the muscles. The tendon is the band of connective tissue that attaches the muscle to the bone. Tendons can be short or long, and are usually rounded. Tendons are slightly elastic and can endure an enormous amount of tension, although they can accidentally stay contracted after exercise, which puts them at a greater risk of being strained. Tendons increase the tensile strength, which leads to sustaining increased loads on the body, and tendons do not tire. Tendons are origin tendons or insertion tendons: Origin tendons: Tendon that attaches the muscle to the least moveable bone. Insertion tendons: Tendon that attaches the muscle to the moveable bone, Ligaments Ligaments are connective tissue, and they attach bones to each other via the joint, or attach cartilage to bone. Ligaments are made of poorly elastic collagen fibre (fibrous protein) and have lots of nerves but limited blood supply. This is the reason that if a ligament is damaged it tends to heal very slowly and often not correctly. There are two types of ligament: 1. Capsular Ligament: Surrounds a joint 2. Collateral Ligament: Supports a joint Ligaments give support to a joint. They are tight to avoid overextension of a joint, or abnormal movement, but they are also flexible to allow movement in the joint. Ligaments that are overextended lose their strength and cause the joint to become unstable. Ligaments work together with the muscles to aid contractions. www.equestricare.com.au  The Soft Tissues Fascia The fascia is the connective tissue that wraps around the entire muscle and is part of every soft tissue in the body. It is thin, white and sheet like. It provides support and protection. Some muscles attach to fascia It acts as a shock absorber and assists movement Like bones, fascia bands are composed primarily of collagen which gives them a tough but pliable texture. The fascial system maintains a balance of tension and elasticity which allows for smooth, unrestricted movement of each muscle group while holding everything in place. If the fascia is restricted then muscle contraction is restricted. Since there is one singular piece of this stretchy, mesh-like substance interweaving through muscles and organs from head to toe like shrink-wrap, distress in one area can affect movement and create symptoms elsewhere. And, like a glove, fascia has enough substance to hold shape, but not enough to support weight. This illustrates how movement and structure conditions, such as poor posture, affect fascia, causing pain and unstable movement. www.equestricare.com.au  The Soft Tissues Muscles Muscles consist of an origin (attachment close to the centre) and an insertion (attachment further from the centre) as well as the belly which is the bulk of the muscle. Muscles contract when they work, and the type on contraction determines the name. Ie. Extensor, flexor etc.. Most muscles are paired (ie. One on the left and one on the right.) Muscles need stimulation by nerve impulses in order to work. There are three types of muscle: 1. Theheart 2. Smooth Muscle – which is the walls of the organs 3. Striated Muscle – muscle that moves the bones Horses have over 700 skeletal muscles, which account for 40-60% of the bodyweight. But don’t worry; we will only be looking at a few of them! Below the hock and carpal joint horses have no muscle and only tendons and ligaments. The contraction of muscles and corresponding articulation of joints are what is responsible for movement in horses. There are three types of muscle contraction. 1. Concentric Contraction: The shortening of a muscle. 2. Eccentric Contraction: The elongation of a muscle. 3. Isometric Contraction: The contraction of a muscle without movement. www.equestricare.com.au  The Body Systems Cardiovascular System The cardiovascular system is composed of the heart, blood, arteries, veins and capillaries. A horse carries about 34-40 litres of blood at any one time. Blood is composed of red (erythrocytes) and white blood (leukocytes) cells (1/3) and liquid (plasma). Red blood cells are produced in bone marrow and are responsible for transporting oxygen to tissues and removing carbon dioxide. White blood cells are responsible for defense against pathogens. Plasma suspends the blood cells and contains clotting agents. It is the liquid element that consists of water, protein, glucose, lipids, salts, enzymes, hormones and antigens. Blood is pumped around the body via the heart. The heart of an average size horse weighs approximately 3.6-4kg and has four chambers. 1. Left atrium 2. Right atrium 3. Left ventricle 4. Right ventricle Blood enters via the left atrium into the left main chamber then it moves through the aorta into the body. A horse’s heart keeps growing until they are about 4yrs of age! Did you know Phar Lap’s heart weighed 6.4kg and Secretariats weighed 10kg!! Blood is supplied to the muscles and organs through arteries and veins. Arteries carry blood from the heart, veins carry blood to the heart Horses have lots of arteries, but the main ones are: ·Aorta – carries blood to the body ·Brachiocepahlic – carries blood to the head and forelegs ·Coeliac – carries blood to the stomach, liver and spleen ·Pulmonary – carries blood to the lungs ·Mesenteric – carries blood to the intestines ·Renal –carries blood to the kidneys ·Iliac – carries blood to the hindquarters www.equestricare.com.au  The Body Systems Cardiovascular System Functions of blood include: Immunity Defence Temperature regulation Waste removal Transport of nutrients and oxygen Transport of endocrine secretions Regulation of water content Regulation of acidity The heart rate of a horse is made by the pumping of the blood. Heart rate is measured via the pulse. The pulse rate of an average sized horse at rest is 28-45 beats per minute. Heart rate increases when the horse is in exercise, or experiencing excitement, nervousness, dehydration, fever, infection or shock. www.equestricare.com.au  The Body Systems Lymphatic System The lymphatic system supports the body’s immune system and is composed of the lymph nodes and lymph vessels. The lymphatic system is a waste removal system that also recovers, filters and recycles tissue fluid in the lymph nodes. All lymph vessels lead to lymph nodes where white blood vessels eliminate waste products. Horses have 31 lymph nodes, but the main ones we are concerned with are the mandibular lymph node, parotid lymph node, superficial cervical nodes, nuchal node, iliac and subiliac nodes. Lymph fluid is composed of: Water Salts Proteins Fats Minimal blood cells The best function of the lymph nodes is when there is inflammation present. When inflammation is present the lymph vessels transport the excess fluid to the nearest lymph node where the waste products from whatever is causing the inflammation are filtered out. The purified fluid is then put back into the blood vessels. In case of infection, the lymph nodes cannot cope and they fill up with debris. You are able to feel them and see them at this point. The one down side of the lymphatic system is that it has no pump.Therefore it is a slow process and one that is supported by the horse’s movement. This is often why when a horse is stabled for long periods of time it gets filling in the legs. This filling is lymph fluid that is unable to be moved around the body without the horse’s movement. www.equestricare.com.au  The Body Systems Respiratory System The respiratory system is composed of the nose, mouth, pharynx, trachea, bronchial tubes and of course the lungs. Breathing enables the horse to get oxygen into it’s system, which is necessary for the horse to stay alive. Breathing or respiration is composed of two parts: 1. Inspiration – Air is breathed in through the nostrils, into the nasal passages (lined with mucous membranes) where it is warmed and cleaned. It then continues into the larynx and trachea.The trachea divides into two bronchi that branch into smaller bronchioli and end as alveoli.Exchange of gasses takes place here. The most important breathing muscle is the diaphragm, which separates the chest cavity from the abdomen During inspiration the diaphragm flattens, creating more room in the chest and lungs. 2. Expiration – The lungs allow the air to escape while the diaphragm returns to it’s normal shape. Respiration rate of horses vary but is approximately 8-12 breaths per minute. Notes: The horse does not breathe through it’s mouth like a human, it only breathes through it’s nostrils.. www.equestricare.com.au  The Body Systems Digestive System The digestive system is composed of the mouth, pharynx, esophagus, stomach, small intestine, large intestine, caecum and anus. It converts food into energy for the body to use. Eating starts with the teeth, and horses at maturity have 36 permanent teeth (not including canines or wolf teeth). Horses tear off grass with their incisors, it is pushed between the molars where it is broken down and chewed. After chewing the food and mixing it with saliva it is swallowed. The food passes the larynx and reaches the esophagus, where it is transported to the opening of the stomach. The entrance of the stomach only allows food to pass in one direction. From the stomach the food moves to the small intestines.Firstly the duodenum where pancreatic juices and bile from the liver is added to the food. From the small intestines it reaches the caecum where it is fermented. Once the food is fermented it moves on to the large intestine where any nutrients are absorbed, then into the rectum and out the anus as manure. Notes: Horses do not vomit, because the stomach only allows food in. The stomach can only hold 12 litres of food, so overload can lead to colic. Horses, like humans produce bile, but they do not have a gall bladder!. www.equestricare.com.au  The Body Systems Nervous System The nervous system of the horse is composed of the brain, spinal cord, nerves, nerve fibres and nerve cells (sensory and motor neurons). It is the control mechanism of the body. The brain is approximately 1% of the horses bodyweight so it is not very big (about 500g). The brain is protected by the bones of the skull, but also by a protective membrane, the meninges, which also provide nutrients to the brain. There are three meninges that surround the brain: 1. Dura mater 2. Arachnoid 3. Pia mater The brain is divided into three areas, that are further divided: 1. Forebrain a. Cerebrum – controls memory and receives sensory information. b. Hypothalamus – controls the internal environment of the horse (homeostasis). c. Thalamus – provides brain with information about internal and external environments. d. Olfactory – sense of smell 2. Midbrain – the smallest area of the brain responsible for passing on information. 3. Hindbrain a. Cerebellum – controls balance b. Medulla oblongata – communication link between the brain and spinal cord. c. Pons – connects the right and left hemispheres of the brain www.equestricare.com.au  The Body Systems Nervous System The horse has three nervous systems: 1. Central Nervous System (CNS) – This is the centre of all control and consists of the brain and spinal cord. 2. Peripheral Nervous System – This governs the nerves that are located outside of the CNS. The peripheral nervous system contains 12 pairs of cranial nerves and 42 pairs of spinal nerves. It has: a. Sensory Nerves – Carry information from the body to the CNS b. Motor Nerves – Carry information from the CNS to the body. 3. Autonomic Nervous System – This is part of the peripheral nervous system but controls the involuntary systems such as circulation, respiration etc.. It has two major systems: a. Sympathetic Nervous System – Governs flight or fight reactions. b. Parasympathetic Nervous System – Governs sleeping, digestion, waste elimination and relaxation.. www.equestricare.com.au  The Body Systems Endocrine System Hormones, secreted by the endocrine system, are the chemical messengers that regulate growth, reproduction, digestion and every other function of the body. Functions include: Growth & Development Reproduction Metabolism Digestion Immune responses Behaviour & Emotion The Endocrine system is made up of: Hypothalamus : The main link between the endocrine and nervous systems. ·Regulates hormones ·Maintains equilibrium ·Regulates body temperature ·Controls blood pressure ·Maintains fluid balance ·Regulates appetite and metabolism ·Controls sexual behaviour Pituitary gland: Controls several other glands producing growth hormones, endorphins, antidiuretic hormones and other sex hormones. Thymus: Located between the lungs and fights disease. Thyroid gland: main function is to convert iodine from food into thyroxine. Parathyroids: Controls the level of calcium Pancreas: secretes digestive juices, insulin and glucagons which control sugar levels. Adrenal glands: There is an adrenal gland on each kidney. They secrete cortisol which is the main stress hormone and adrenalin. Ovaries: Produce the two female hormones progesterone and oestrogen. Testes: Produce testosterone. www.equestricare.com.au  The Body Systems Urinary System The urinary system: Filters the blood Controls the amount of fluid in the body Removes waste The urinary system consists of: Kidney’s - Cleanse the blood, remove toxins and excrete liquid waste Ureters - carries liquid waste (urine) from the kidney’s to the bladder Bladder - 4.5litres. stores liquid waste (urine) Urethra - evacuates liquid waste (urine) from the body Reproductive System. The Mare’s reproductive system is made up of: Ovaries: Produce oestrogen which is responsible for releasing the egg. Fallopian Tubes: Where the egg is fertilised. Lined by cillia Uterus: Where the embryo develops Cervix: The neck of the womb Vagina: The area where the penis enters and the foal is born through. Vulva: External opening of the vagina. The stallions reproductive system is made up of: Testes: Produce sperm and testosterone Scrotum: Suspends the testes at 4-7 degrees Accessory glands: Produce semen. Glands are vesicular, prostrate and bulbourethral. Penis: the male organ of reproduction.. www.equestricare.com.au  Senses Sight Humans are predators and our eyes are situated in the middle of our face. Horses are prey animals and their eyes are situated on the sides of their heads, so that they can see nearly everything around them without having to move their head!Horses can detect the smallest movement miles away, but they struggle to focus on close objects. Horses see colours differently to humans, but what those colours are is debatable. Notes: Why do horses shy?Horses have two types of vision – monocular (sees a different image with each eye) and binocular (views the same image with both eyes). When you are riding past a stationary object and the horse moves it’s head it can change the field of vision causing the object to jump! Sound Horses, unlike humans, have very mobile ears. These ears can be turned every which way, and their hearing is very sensitive. The size and sensitivity of the horses. ears allow them to detect a very wide range of sounds. Horses ears are part of their body language. There are three parts to the ear: 1. External ear (pinna) – part that can be seen. It has 16 muscles alone, and can be turned 180 degrees. 2. Middle ear – mucous lined cavity which transmits the soundwaves and contains the ear drum and Eustachian tubes. 3. Inner ear – deep within the ear it contains the cochlea and semi-circular canals. Touch Horses are very sensitive to touch. They have extremely sensitive skin covered in.receptor cells and the muzzles have tactile hairs and vast numbers of nerve endings. The nerve endings under the skin are very sensitive and can detect the slightest sensation, like a fly landing on the skin. The skin is divided into three layers: 1. Epidermis – outer layer of the skin which can be seen under the hair. 2. Dermis – middle layer consisting of the arteries, veins, nerve neurons, hair follicles, erector muscles and sweat glands. 3. Subdermal layer – subcutaneous fat which stores some nutrients and joins the skin to the underlying tissues. Smell Horses have very large nasal cavities and a much better sense of smell then humans. Did you know that when a horse “flehmens” it’s not showing distaste at a smell but actually amplifying it?. Taste Taste works hand in hand with sense of smell, as horses need to smell food before they taste it. Horses have very large, mobile tongues, but little is actually known about their taste, aside from it being separated into bitter, sweet, sour and salty.. www.equestricare.com.au  Vocabulary Sometimes the vocabulary used in relation to equine massage sounds like a foreign language….. Some of the time it is!! Here I have included some of the most commonly used prefixes and suffixes in equine massage for you to use as a reference.. www.equestricare.com.au  Terminology Below are some of the most commonly used terms in muscles, bones and movement.. www.equestricare.com.au www.equestricare.com.au