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The Anatomy Of A Horses Hoof

Posted by Nicole Nauss on January 27, 2014 at 6:10 PM Comments comments (3)

The Anatomy Of A Horses Hoof

Transitioning barefoot hoof, from below. Details: heel perioplium (1), bulb (2), frog (3), central groove (4), collateral groove (5), heel (6), bar (7), seat of corn (pigmented walls) (external layer) (9), water line (inner layer) (10), white line (11), apex of frog (12), sole (13), toe (14), how to measure width (15), quarter (16), how to measure length (17)



The hoof is made up by an outer part, the hoof capsule (composed of various cornified specialised structures) and an inner, living part, containing soft tissues and bone. The cornified material of the hoof capsule is different in structure and properties in different parts. Dorsally, it covers, protects and supports P3 (also known as the coffin bone, pedal bone, PIII). Palmarly/plantarly, it covers and protects specialised soft tissues (tendons, ligaments, fibro-fatty and/or fibrocartilaginous tissues and cartilage). The upper, almost circular limit of the hoof capsule is the coronet (coronary band), having an angle to the ground of roughly similar magnitude in each pair of feet (i.e. fronts and backs). These angles may differ slightly from one horse to another, but not markedly. The walls originate from the coronet band. Walls are longer in the dorsal portion of the hoof (toe), intermediate in length in the lateral portion (quarter) and very short in palmar/plantar portion (heel). Heels are separated by an elastic, resilient structure named the 'frog'. In the palmar/plantar part of the foot, above the heels and the frog, there are two oval bulges named the 'bulbs'.

When viewed from the lower surface, the hoof wall's free margin encircles most of the hoof. The triangular frog occupies the center area. Lateral to the frog are two grooves, deeper in their posterior portion, named 'collateral grooves'. At the heels, the palmar/plantar portion of the walls bend inward sharply, following the external surface of collateral grooves to form the bars. The lower surface of the hoof, from the outer walls and the inner frog and bars, is covered by an exfoliating keratinised material, called the 'sole'.

Just below the coronet, the walls are covered for about an inch by a cornified, opaque 'periople' material. In the palmar/plantar part of the hoof, the periople is thicker and more rubbery over the heels, and it merges with frog material. Not all horses have the same amount of periople. Dry feet tend to lack this substance, which can be substituted with a hoof dressing.


Characters and functions of the external hoof structures

 

The Walls

The walls are considered as a protective shield covering the sensitive internal hoof tissues (like the exoskeleton of arthropods), as a structure devoted to dissipating the energy of concussion, and as a surface to provide grip on different terrains. They are elastic and very tough, and vary in thickness from 6 to 12 mm. The walls are composed of three distinct layers: the pigmented layer, the water line and the white line.

The pigmented layer is generated by the coronet, and its color is just like that of the coronet skin from which it is derived. If the coronet skin has any dark patch, the walls show a parallel pigmented line, from the coronet to the ground, showing the wall's growth direction. This layer has predominately protective role, and is not as resistant to ground contact, where it can break and flake away.

The water line is built up by the coronet and by the wall's corium (the living tissue immediately beneath the walls). Its thickness increases proportionally to the distance from the coronet and, in the lower third of the walls, is thicker than the pigmented layer. It is very resistant to contact to the ground, and it serves mainly a support function.

The white line is the inner layer of the wall. It is softer and fibrous in structure and light in color; white in a freshly trimmed hoof, yellowish or gray after exposure to air and dirt. From the underside of the healthy hoof, it is seen as a thin line joining the sole and the walls. The white line grows out from the laminar connections. Any visible derangement of the white line indicates some important derangement of laminar connections that fix the walls to the underlying P3 bone. Since the white line is softer than both the walls and the sole, it wears fast where it appears on the surface; it appears as a subtle groove between the sole and the walls, often with some debris or sand inside.

The three layers of the wall merge in a single mass and they grow downwards together. If the wall does not wear naturally, from sufficient movement on abrasive terrains, then it will protrude from the solar surface. It then becomes prone to breakage, and the healthy hoof will self-trim, by breaking or chipping off.

When a horseshoe is applied, it is fixed to the wall. Nails are driven in, oblique to the walls. They enter the wall at the outside edge of the white line and they emerge at the wall's surface, about 15 to 20 mm from the base of the wall.

The wall is anatomically analogous to the human finger or toe nail.


The Frog

The frog is a V shaped structure that extends forwards across about two-thirds of the sole. Its thickness grows from the front to the back and, at the back, it merges with the heel periople. In its midline, it has a central groove (sulcus), that extends up between the bulbs.

It is dark gray-blackish in color and of a rubbery consistency, suggesting its role as shock absorber and grip tool on hard, smooth ground. The frog also acts like a pump to move the blood back to the heart, a great distance from the relatively thin leg to the main organ of the circulatory system.

In the stabled horse, the frog does not wear, but degrades, due to bacterial and fungal activity, to an irregular, soft, slashed surface. In the free-roaming horse, it hardens into a callous consistency with a near-smooth surface.

It is anatomically analogous to the human fingertip.


The Sole

The sole has a whitish-yellowish, sometimes grayish color. It covers the whole space from the perimeter of the wall to the bars and the frog, on the underside of the hoof. Its deep layer has a compact, waxy character and it is called 'live sole'. Its surface is variable in character as a result of ground contact. If there is no contact, as in shod hooves or when the walls are too long or the movement poor, the lower surface of the sole has a crumbly consistency, and it is easily abraded by scratching it with a hoofpick. Conversely, it has a very hard consistency, with a smooth, bright surface, when there is a consistent, active contact with the ground. The front portion beneath the front of the pedal bone is called the 'sole callus'.

A stone bruise affects the sole of the horse's foot. It is often caused by a horse treading on a stone or sharp type of object, landings from high jumps and excessive exposure to snow. A major symptom is lameness.


The Bars

Bars are the inward folds of the wall, originating from the heels at an abrupt angle. The strong structure built up by the extremity of the heel and of the bar is named the 'heel buttress'. The sole between the heel walls and the bars is named the 'seat of corn', and it is a very important landmark used by natural hoof trimmers to evaluate the correct heel height. The bars have a three-layer structure, just like the walls. When overgrown, they bend outwards and cover the lower surface of the sole.

Internal Structures

The third phalanx (coffin bone; pedal bone; P3 is completely (or almost completely) covered by the hoof capsule. It has a crescent shape and a lower cup-like concavity. Its external surface mirrors the wall's shape. The corium, a dermo-epidermal, highly vascularized layer between the wall and the coffin bone, has a parallel, laminar shape, and is named the laminae. Laminar connection has a key role in the strength and the health of the hoof. Beneath the rear part of the sole, there is the digital cushion, which separates the frog and the bulb from underlying tendons, joints and bones, providing cushioning protection. In foals and yearlings, the digital cushion is composed of fibro-fatty, soft tissue. In the adult horse, it hardens into a fibro cartilagineous tissue when sufficient, consistent concussion stimulates the back of the hoof. Normal transformation of the digital cushion into fibrocartilagineous tissue is now considered a key goal, both for prevention of, and for rehabilitation of recovering cases of navicular syndrome. The flexor tendon lays deeper, just along the posterior surface of the small pastern bone (PII) and navicular bone, and it connects with posterior surface of P3; the navicular functions as a pulley.

   Sagittal section of a wild horse hoof. Pink: soft tissues; light gray: bones (P2, P3 and navicular bone); blue: tendons; red: corium; yellow: digital cushion; dark gray: frog; orange: sole; brown: walls)


Disorders

 

There are several disorders and injuries that can affect the equine hoof. Laminitis and Navicular Disease are two of the most serious. Thrush, a common bacterial infection, can become serious if left untreated. Quiltor, an infection of the lower leg that can travel under the hoof, is also sometimes seen, although most commonly in draft horses.

Quarter cracks are vertical splits in a hoof wall, most commonly seen on the inside of the front hooves or the outside of the hind hooves. They can result from poor shoeing and management practices, natural hoof conformation, or injuries to the leg and hoof.



Parts Of The Horse's Body

Posted by Nicole Nauss on January 24, 2014 at 9:55 PM Comments comments (0)


1. Muzzle - The part of the head which includes the nostrils, lips, and the bones, gums, and teeth covered by latter.
2. Nostril -  Large nostrils allow for the intake of large quantities of air, especially while running. Horse also use scent to help identify people, animals and objects. Objects that are too close to a horse’s face to see will probably get a thorough sniffing. Some horses display their              emotions with the nostrils. Some horses will wrinkle their nose in disgust. Entrance to the respiratory system.
3. Cheek - The wide flat area on the side of the face is the cheek, with the rim of the bone curved along the bottom. Also Known As: cheek bone, jowl.
4. Face - The front part of the head.
5. Eye - In which a horse can see. Horses have dichromic vision, meaning they have a fundamentally different view of the world to people.
6. Forelock - A lock of hair that grows from or falls on the forehead,  the part of a horse's mane that falls forward between the ears.
7. Ears - In which to hear. Is a primary sourse of noticing a horses behavior in also, what it is thinking or listening towards something.
8. Poll - The poll is the area immediately behind the ears and the underlying bones are the top of the skull bone and the atlas bones of the neck. In this area are many nerve endings and acupressure points. The poll area is where the bridle path, if one is clipped, begins. On some     horses the poll is quite flat, while on others it may be more prominent.
9. Mane -  The long coarse hair that grows from the crest of the neck.
10. Crest - The crest is the topline of the neck. Ideally the crest should be a gentle convex curve from the poll to the withers. On a very fat horse the crest can be very thick, and almost seem to flop over. On a very thin horse the crest will be straight and thin. Some breeds like Morgans,       Arabians, some warmbloods and draft horses and ponies have a more distinctively crest than breeds like Quarter Horses and Thoroughbreds.
11. Withers - The withers are at the top of the shoulder where the neck joins the body. The ‘lump’ seen on many horses is the top of the spiny process of the tallest thoracic vertebrae. This part of the vertebrae is quite high on some horses and shallow on others.
12. Back - Part of the horse where the saddle is laid upon.
13. Loin - The region where the back ends is the loin. This can be a very sensitive area on some horses. The horse would buck if you slid back and sat on its loins.
14. Croup - The croup is the area from the highest point of the hindquarters to top of the tail.
15. Dock - The area at the top of the tail is called the dock. Below the skin are muscles and the extension of the vertebrae from the spine. There are about 15 small vertebrae that make up the bone structure of the tail. The muscles through the dock and tail make the tail very mobile for       both expressing mood, balancing, and swishing away insects.
16. Buttock -  Fleshy part under the tail. 
17. Thigh - Upper part of the rear leg.
18. Tail - Extension of the spinal column in which long hair grows from.
19. Stifle - Part of the leg of a horse between the thigh and the kneecap. The stifle joint is both very large and very complex in structure.
20. Gaskin - The part of the hind leg of a horse or related animal between the stifle and the hock.
21. Hock - Point of the part of the gaskin behind the knee.
22. Chestnuts - Also known as a night eye, is a callousity on the body of a horse or other equine, found on the inner side of the leg above the  knee on the foreleg and, if present, below the hock on the hind leg.
23. Cannon Bone - The greatly developed middle metacarpal or metatarsal bone of hoofed quadruped mammals, extending from the hock to the fetlock.
24. Fetlock - The fetlock is formed by the joint between the canon bone and the longer pastern bone. At the back of the fetlock lies a small bone called the sesamoid. Occasionally, you may hear the fetlock joint referred to as the pastern joint or ankle.
25. Pastern - Part of the horse that corresponds to the first phalange. The pastern is made up of two bones that extend downwards from the fetlock. The upper bone is longer and the shorter lower bone extends into the hoof where it joins to the pedal bone inside.
26. Coronet Band -  Upper part of a horse's hoof. The ring of soft tissue just above the horny hoof that blends into the skin of the leg
27. Hoof - Developed nail that enclosed the end of the toes of a horse.
28. Point Of Hip - Joint connecting the rear leg to the pelvis.
29. Sheath - The pocket of skin that protects the penis of the horse.
30. Flank - The slightly indented area behind the area of the barrel is the flank. This is the area you watch to count your horse’s respiration. If the flank appears unusually sunken this can mean your horse is dehydrated.
31. Ribs - Integral to the back structure is the rib cage, which also provides support to the horse and rider. Here you can tell if a horse is underweight by thier ribs showing.
32. Heart Girth - The measurement taken around the horse's barrel just behind the front legs.
33. Elbow - The joint of the front leg at the point where the belly of the horse meets the leg.
34. Shoulder -  Made up of the scapula and associated muscles, runs from the withers to the point of shoulder (the joint at the front of the chest, i.e. the glenoid); the angle of the shoulder has a great effect on the horse's movement and jumping ability, and is an important aspect      of equine conformation.
35. Point Of Shoulder - The shoulder should be long, sloping, and muscular. It should extend well into the back.
36. Arm - Front leg coming from the shoulder.
37. Forearm - The area of the front leg between the knee and elbow, consisting of the fused radius and ulna, and all the tissue around these bones; anatomically, the antebrachium. 
38. Knee - The carpus of the horse (equivalent to the human wrist), the large joint in the front legs, above the cannon bone.
39. Chest - When viewed from the front the chest of the horse should be well defined and not blend into the bottom of the neck. The width of the      chest is defined by the structure of the bone beneath it.
40. Throat Latch - The point at which the windpipe meets the head at the underside of the jaw, corresponding to where the eponymous part of a bridle goes.
41. Chin Groove - The part of the horse's head behind the lower lip and chin, the area that dips down slightly on the lower jaw; area where the curb chain of certain bits is fastened.
42. Neck - Part of the horse between the head, the withers and the chest.

 



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