or

Lamina [L.], A thin flat layer or membrane.

itis [Gr.], Suffix meaning inflammation of.

Laminitis is a malady affecting the horse's foot. There are many causes of laminitis. Most of the laminitis we see is called Alimentary laminitis. Each different cause may be called by many other names. For example, one form of alimentary laminitis might be called grass founder , another called grain-binge. A mare who has not discharge all of the placenta after giving birth is at risk of getting laminitis, some call this retained placenta, while others might call this metritis. The important thing to know is that there are many reasons a horse might get laminitis and many different names people will use when they talk about it.

The reason we are so concerned about laminitis is that it can leave permanent scars in the horse's feet. Laminitis will affect each horse differently (even each foot of the same horse), from the barely noticeable case to the fatal case. It is important to think of laminitis as a symptom of other problems the horse is experiencing. Because we become aware of laminitis through the lameness it produces in the feet, if we only fix the feet we are ignoring the real problem, and the lameness may come back.

Laminitis means inflammation of the laminae. The Laminae (pronounced Lamin-nee) are the tissues that connect the hoof wall to the Coffin Bone. The Laminae are arranged in vertical rows beginning at the Hair line, or Coronary Band, continuing down to the ground. The largest percentage of Laminae are in the front or Anterior region of the hoof, where they are longest. They gradually become shorter as they approach the heels. The hoof has Sensitive and Insensitive Laminae. The Laminae connected to the hoof wall are the Insensitive Laminae. The Laminae connected to the Coffin Bone are the Sensitive Laminae. The Sensitive Laminae are vascular and innervated. The Sensitive and Insensitive Laminae Interdigitate.

Laminitis is often confused with Acute Laminitis or Founder. Founder, which is a maritime term meaning sink, means that the Sensitive Laminae holding the Coffin Bone in place are letting go. In mild cases of Laminitis we are not always aware of it's presence. As inflammation (Laminitis) increases, Edema accompanies it. At this point we may begin to see lameness. Because the Laminae are between a rock and a hard place (the hoof wall and the Coffin Bone) they have nowhere to expand to accommodate the edema. So Lamellar edema displaces the blood in the Capillariesof the Sensitive Laminae causing Pressure Ischemia. If the Ischemia persists it causes the Laminae to die. This is called Acute Laminitis or Founder.

The Laminae in the front of the hoof, which carry most of the weight of the horse, will stretch and tear allowing the front part of the coffin bone to pull away from the hoof wall. This allows the Distal Border of the Coffin bone to drop to varying degrees. This is called "Rotation" (measured in degrees). In severe cases all the Laminae die, allowing the Coffin Bone to drop right through the bottom of the hoof. This is called Vertical Displacement or "Sinker". We can say a horse has "Foundered" when either Rotation or Vertical Displacement has occurred.

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Alimentary: Concerned with food, nutrition, or digestion.

Anastomose: To communicate directly or by means of connecting channels, said of blood and lymph vessels and nerves.

Anterior: Located on or near the front of an organ.

Drawing of hoof's Anterior Surface.

Anoxia: Deficiency of oxygen.

AVA: AVA's Are Arteriovenous-anastomosis. Anastomosis between an artery and a vein by which the capillary bed is bypassed.If you want to know more about them check outDr. Pollitt's articles

Capillary: Any of the minute blood vessels that connect the smallest arteries(arterioles) to the smallest veins(venules). They form an anastomosing network (AVA's) throughout the body which brings the blood into intimate relationship with the tissue cells.

The ability of substances to diffuse through capillary walls (by way of capillary pores) into the tissue spaces is called Capillary permeability. It is influenced by anoxia, adrenal cortical hormone, and a bunch of other stuff.

Their wall consists of a single layer of squamous cells called endothelium through which blood and oxygen diffuse to the tissue and products of metabolic activity enter the blood stream. They are capable of being constricted so as to have almost no lumen at all. They are also capable of being dilated.

The Aorta is a Big Mother, Capillaries are Little Suckers.

Detailed Illustration of the little suckers.

Coffin Bone: Third Phalange, PIII, Pedal bone, the last bone of the leg.

Spectacular Graphic of PIII

When I get it together I will put a real definition here too.

Distal: Farthest from the center, from the medial line, or from the trunk. Opposed to Proximal

Distal Border: The Distal Border of PIII is the lowest part of PIII. The crescent shaped part that is the bottom of the front of PIII.

If the Laminae of the toe stretch enough the Distal border of PIII can descend, crushing capillaries lying between it and the Horny Sole. Thus causing Symmetrical Subsolar Hematomas. In this case the hematoma is not the result of capillary crushing between PIII and the ground, but rather, between PIII and the inside of the Horny sole. A steel plate bolted to the ground surface of a shoe will not prevent this type of bruise.

Graphic showing Symmetrical Subsolar Hematomas.

Graphic showing Distal Border of PIII

Edema: an excessive accumulation of serous fluid in tissue spaces or a body cavity.

May result from increased permeability of the capillary walls do to vasoactive substances (kinins; Bradykinin), inflammatory conditions, chemical toxins, histamine, etc. Or increased capillary pressure due to venous obstruction.

Edematous: pert. to, or affected with, edema.

Stunning Illustration of Edema

Endothelium: A form of squamous epithelium consisting of flat cells which line the blood and lymphatic vessels, the heart, and various other body cavities. Derived from mesoderm.

Grain-binge: A grain-binge is when a horse gets into the grain storage and eats until he pops.

Grass-founder: Grass founder is when a horse eats too much grass.

This usually happens in the spring when the grass is particularly rich, but it can happen anytime.

Horses have differing tolerances to various feeds, so it is a good idea to become familiar with your horse's tolerance to his feeds.

Hematoma: A mass of blood (often clotted) confined to a tissue or a space, and caused by a break in a blood vessel. A bruise

Interdigitate: Interlocking of toothed or finger like processes.

Two hands with fingers Interdigitating!

Ischemia: Local and temporary deficiency of blood supply due to obstruction of the circulation.

Lumen: The space within a an artery, vein, intestine, or tube.

Malady: A disease, a disorder, or an ailment.

Metritis: Inflammation of the uterus. See Placenta.

Pedalosteitis: Inflammation of the pedal bone (Coffin bone, P₃). Resulting from

Placenta: A membranous vascular organ that develops in female mammals during pregnancy, lining the uterine wall and partially enveloping the fetus, to which it is attached by the umbilical cord. Following birth, the placenta is expelled.

Sometimes not all of the placenta is expelled. Pieces that remain can cause inflammation and infection. This can lead to laminitis. The placenta should be examined to see that it has all been expelled, if pieces are missing the uterus should be flushed by the veterinarian.

Serous: having the nature of serum.

Serum: The watery portion of the blood after coagulation.

Squamous: Scale like.

Squamous cell: Flat, scaly, epithelial cell.

Symptom: A characteristic sign or indication of the existence of something else.