Lecture 9- Comparative histology of the hoof Flashcards
Hoof
Cornfield covering of the distal end of the digit of ungulates, modification of skin, true organ
Perissodactyl hoof
Odd toed Ex: horse
Artiodactyl
Even toed, ex: cow
Claw and nails
Partial cornifications that enclose part of the 3rd phalanx, skin appendage
What layers make up the epidermis
Stratum corneum, stratum granulosum, stratum spinosum, and stratum basal
What does the epidermis comprise in the hoof
Hoof capsule
What is the dermis made of
Papillary and reticular regions
What does the dermis make up in the hoof
Corium
What is the hoof capsule
Epidermis, germinative, proliferative, and keratinized layers
What is the corium
Dermis, innervated and vascularized layer
What cells do the stratum basale have
Stem cells
What cells does the stratum spinosum have
Proliferative cells
What cells does the stratum granulosum make
Partially keratinized cells
What cells does the stratum core num make
Fully keratinized cells
Periople
Zone of transition from the skin to the hoof
Where are the periploic and coronary grooves
Run at the proximal border of the wall
What constitutes the solar surface of a horse hoof
Sole and frog
What does the frog look like
Triangular and irregular region
Corium is continuous with ____
Dermis of limb skin, single layer with different zones
What are the three corium at the wall
Periploic, coronary, laminar
Hoof wall and order from outer to inner
Made of different strata
Outer to inner:
Stratum externum, outer stratum medium, inner stratum medium, stratum internum, corium
What is the area of overlapping between the corium and hoof capsule
Stratum internum
What stratum is the perioplic corium associated with and how is it made
Stratum externum
Perioplic corium is associated with proliferative cells which eventually get keratinized and give off stratum externum
What stratum’s is the coronary corium associated with and how is it made
Outer stratum medium and inner stratum medium
Stem cells associated with coronary corium and form these outer and inner stratum medium
What stratum is the laminar corium associated with and how is it made
Stratum internum
Stem cells here are inactive
Where does hoof growth take place
Stratum externum, outer and inner stratum medium
Perioplic and coronary corium
Does not take place from inner to outer regions, extends distally
What regions belong to the papillary type of corium
Perioplic and coronary regions that are associated with hoof growth
What regions of the corium provide support, nutrients and oxygen to adjacent stem cells
Perioplic and coronary regions so they can produce additional keratinized tissue to replace the one lost during locomotion
What do they papillary corium contain
Papillae
What is the area between papillae
Inter-papillary region
The wall contains tubular structures called ____ that are embedded by compact keratinized tissue ____
Tubular hoof and intertubular hoof
What produces the tubular hoof
Stratum basale
What produces the inter-papillary region
Intertubular hoof
Where are the proliferative cells located in the hoof wall
Surface of papillae and inter-papillary region
What do the differentiating cells on the papillae generate
Tubular hoof
What do the differentiating cells on the inter-papillary region generate
Inter-tubular ones
The cells are the tip of the papillae break down and leave space for ___
Tubular horn
What does rhodamine stain allow for
Observation of keratinized area, everything below line is rhodamine positive cells in the stratum corneum (keratinized) and the rhodamine negative cells in the stratum basale
Keratinization is below papillae and non-keratinized area exists between stem cells and keratinized cells
What two structures interlock in the hoof wall
Laminar corium (dermal lamellae)interlocks with the epidermal lamellae to suspend the distal phalanx within the hoof capsule
What does the interlocking of the dermal and epidermal lamellae form
Stratum internum of the wall, generates important suspensory apparatus that makes the attachment of the capsule and corium efficient
What two structures does the laminar corium attach to
Periosteum of PIII and perichondrium of lateral cartilages, completes suspensory apparatus that attaches wall to skeleton
Secondary lamellae
Present on epidermal and dermal lamellae that increase surface area for attachment
What cells are located on the surface of the secondary dermal lamellae
Stem cells (stratum basale)- normally quiescent only active to heal wounds at wall
What is the primary function of the stratum internum
Create the suspensory apparatus for the 3rd phalanx and its associated structures
Corium and sole belong to the ____ type
Papillary type and therefore associated with regions for distal hoof growth
What is the main difference between the papillae of the sole and frog vs perioplic and coronary
The papillae of sole and frog are shorter and more homogenous
Where does the corium of the sole and frog attach
Periosteum of the solar surface of the third phalanx, except at bulbs where it becomes the digital cushion
What is the digital cushion made of
Fat and fibroelastic connective tissue
At the union of the wall and sole what replaces the laminar corium and produces full keratinization of the stratum internum
Papillary corium (terminal papillae)
What doe the stem cells on the terminal papillae do
Generate new hoof between the epidermal lamellae, therefore the stratum internum gets fully keratinized and closes the gap between the wall and sole
Zona alba/linea alba ungulate
Stratum internum and inner stratum medium make a poorly pigmented area that can be seen at the union of the sole and wall.
Contains 2 zones- outer ring in the stratum internum and the inner ring in the stratum medium
Describe hoof growth in terms of epidermal and dermal lamellae detachment and reattachment
Hoof grows when non-keratinized cells from papillary corium push down on keratinized cells. This pressure induces expression of matrix metalloproteinases that detach the epidermal and dermal lamellae. The keratinized slide downward on stratum basale and secondary lamellae. Once the pressure is disappeared, the union of the lamellae takes place by secreting metalloproteinases inhibitors
What are the hoof strategies to avoid column rupture
- Intertubular horn reduces fragility by embedding the tubular horn
- Central cavity provides flexibility to tubular horn
- Concentric layers of cells of the tubular horn contribute to flexibility
- The frog provides complementary support with the shorter stronger hoof
- The sole-frog angles open to cushion weight load
Artiodactyl foot lacks what
Frog
What do the epidermal and dermal lamellae lack
Secondary lamellae
In the Artiodactyl hoof what replaces the frog corium and is continuous with the sole corium
Digital pad corium, attaches to the 3rd phalanx, lateral cartilages and digital cushion
Laminitis
Inflammatory process of the dermal lamellae that eventually leads to loss of lamellae interlocking and detachment of 3rd phalanx =
