Fig 3. Transverse section of a pigmented hoof wall (unstained). The intertubular hoof is heavily pigmented and is the strongest component of the hoof wall. In contrast the unpigmented tubules of the hoof wall have a hollow medulla and the mature keratinocytes of the tubular hoof are arranged in concentric layers (x 200).
The intertubular horn is formed at right angles to the tubular horn and bestows on the hoof wall the unique property of a mechanically stable, multidirectional, fibre-reinforced composite (Bertram and Gosline, 1987). Interestingly hoof wall is stiffer and stronger at right angles to the direction of the tubules a finding at odds with the usual assumption that the ground reaction force is transmitted proximally up the hoof wall parallel to the tubules. The hoof wall appears to be reinforced by the tubules but it is the intertubular material that accounts for most of its mechanical strength stiffness and fracture toughness. The tubules are 3 times more likely to fracture than intertubular horn (Leach, 1980; Bertram and Gosline 1986). The stratum medium is considered to have an anatomical design that confers strength in all directions. Unlike bone which is a living tissue and remodels to become stronger along lines of stress the stratum medium is nonliving tissue but is anatomically constructed to resist stress in every direction and to never require remodelling. During normal locomotion the stratum medium only experiences one-tenth of the compressive force required to cause its structural failure (Thomason et al 1992).
The basal cell daughters whether destined to be tubular or intertubular hoof do not keratinize immediately. As the distance between basal cells and their daughters increases (each generation is pushed further away from the basal cell layer by the production of successive generations) the intracellular skeleton of the maturing cells becomes more dense (by the manufacture of more intermediate filaments composed of various keratin molecules). Thus by increasing the number of desmosomes more strong attachment zones are formed between the cell membranes of adjoining keratinocytes. Desmosomes are points of intercellular contact, which function like spot welds between adjacent cells (Fig 4).
Fig 4. Desmosomes (D) are like spot-welds forming tight junctions between adjacent keratinocytes. Intermediate filaments made of keratin molecules form the internal skeleton of the cell and attach to the inner densely staining attachment plaque of the desmosome. Electron micrograph x 15,000.
tAnatomy of the Inner Hoof Walld o Dating Naked yAnatomy of the Inner Hoof Wallx Dating r r Nude Online Dating