Lecture 9- Comparative histology of the hoof

Question 1

Hoof

Answer 1

Cornfield covering of the distal end of the digit of ungulates, modification of skin, true organ

Question 2

Perissodactyl hoof

Answer 2

Odd toed Ex: horse

Question 3

Artiodactyl

Answer 3

Even toed, ex: cow

Question 4

Claw and nails

Answer 4

Partial cornifications that enclose part of the 3rd phalanx, skin appendage

Question 5

What layers make up the epidermis

Answer 5

Stratum corneum, stratum granulosum, stratum spinosum, and stratum basal

Question 6

What does the epidermis comprise in the hoof

Answer 6

Hoof capsule

Question 7

What is the dermis made of

Answer 7

Papillary and reticular regions

Question 8

What does the dermis make up in the hoof

Answer 8

Corium

Question 9

What is the hoof capsule

Answer 9

Epidermis, germinative, proliferative, and keratinized layers

Question 10

What is the corium

Answer 10

Dermis, innervated and vascularized layer

Question 11

What cells do the stratum basale have

Answer 11

Stem cells

Question 12

What cells does the stratum spinosum have

Answer 12

Proliferative cells

Question 13

What cells does the stratum granulosum make

Answer 13

Partially keratinized cells

Question 14

What cells does the stratum core num make

Answer 14

Fully keratinized cells

Question 15

Periople

Answer 15

Zone of transition from the skin to the hoof

Question 16

Where are the periploic and coronary grooves

Answer 16

Run at the proximal border of the wall

Question 17

What constitutes the solar surface of a horse hoof

Answer 17

Sole and frog

Question 18

What does the frog look like

Answer 18

Triangular and irregular region

Question 19

Corium is continuous with ____

Answer 19

Dermis of limb skin, single layer with different zones

Question 20

What are the three corium at the wall

Answer 20

Periploic, coronary, laminar

Question 21

Hoof wall and order from outer to inner

Answer 21

Made of different strata
Outer to inner:
Stratum externum, outer stratum medium, inner stratum medium, stratum internum, corium

Question 22

What is the area of overlapping between the corium and hoof capsule

Answer 22

Stratum internum

Question 23

What stratum is the perioplic corium associated with and how is it made

Answer 23

Stratum externum

Perioplic corium is associated with proliferative cells which eventually get keratinized and give off stratum externum

Question 24

What stratum’s is the coronary corium associated with and how is it made

Answer 24

Outer stratum medium and inner stratum medium

Stem cells associated with coronary corium and form these outer and inner stratum medium

Question 25

What stratum is the laminar corium associated with and how is it made

Answer 25

Stratum internum Stem cells here are inactive

Question 26

Where does hoof growth take place

Answer 26

Stratum externum, outer and inner stratum medium Perioplic and coronary corium Does not take place from inner to outer regions, extends distally

Question 27

What regions belong to the papillary type of corium

Answer 27

Perioplic and coronary regions that are associated with hoof growth

Question 28

What regions of the corium provide support, nutrients and oxygen to adjacent stem cells

Answer 28

Perioplic and coronary regions so they can produce additional keratinized tissue to replace the one lost during locomotion

Question 29

What do they papillary corium contain

Answer 29

Papillae

Question 30

What is the area between papillae

Answer 30

Inter-papillary region

Question 31

The wall contains tubular structures called ____ that are embedded by compact keratinized tissue ____

Answer 31

Tubular hoof and intertubular hoof

Question 32

What produces the tubular hoof

Answer 32

Stratum basale

Question 33

What produces the inter-papillary region

Answer 33

Intertubular hoof

Question 34

Where are the proliferative cells located in the hoof wall

Answer 34

Surface of papillae and inter-papillary region

Question 35

What do the differentiating cells on the papillae generate

Answer 35

Tubular hoof

Question 36

What do the differentiating cells on the inter-papillary region generate

Answer 36

Inter-tubular ones

Question 37

The cells are the tip of the papillae break down and leave space for ___

Answer 37

Tubular horn

Question 38

What does rhodamine stain allow for

Answer 38

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

Question 39

What two structures interlock in the hoof wall

Answer 39

Laminar corium (dermal lamellae)interlocks with the epidermal lamellae to suspend the distal phalanx within the hoof capsule

Question 40

What does the interlocking of the dermal and epidermal lamellae form

Answer 40

Stratum internum of the wall, generates important suspensory apparatus that makes the attachment of the capsule and corium efficient

Question 41

What two structures does the laminar corium attach to

Answer 41

Periosteum of PIII and perichondrium of lateral cartilages, completes suspensory apparatus that attaches wall to skeleton

Question 42

Secondary lamellae

Answer 42

Present on epidermal and dermal lamellae that increase surface area for attachment

Question 43

What cells are located on the surface of the secondary dermal lamellae

Answer 43

Stem cells (stratum basale)- normally quiescent only active to heal wounds at wall

Question 44

What is the primary function of the stratum internum

Answer 44

Create the suspensory apparatus for the 3rd phalanx and its associated structures

Question 45

Corium and sole belong to the ____ type

Answer 45

Papillary type and therefore associated with regions for distal hoof growth

Question 46

What is the main difference between the papillae of the sole and frog vs perioplic and coronary

Answer 46

The papillae of sole and frog are shorter and more homogenous

Question 47

Where does the corium of the sole and frog attach

Answer 47

Periosteum of the solar surface of the third phalanx, except at bulbs where it becomes the digital cushion

Question 48

What is the digital cushion made of

Answer 48

Fat and fibroelastic connective tissue

Question 49

At the union of the wall and sole what replaces the laminar corium and produces full keratinization of the stratum internum

Answer 49

Papillary corium (terminal papillae)

Question 50

What doe the stem cells on the terminal papillae do

Answer 50

Generate new hoof between the epidermal lamellae, therefore the stratum internum gets fully keratinized and closes the gap between the wall and sole

Question 51

Zona alba/linea alba ungulate

Answer 51

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

Question 52

Describe hoof growth in terms of epidermal and dermal lamellae detachment and reattachment

Answer 52

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

Question 53

What are the hoof strategies to avoid column rupture

Answer 53

1. Intertubular horn reduces fragility by embedding the tubular horn 2. Central cavity provides flexibility to tubular horn 3. Concentric layers of cells of the tubular horn contribute to flexibility 4. The frog provides complementary support with the shorter stronger hoof 5. The sole-frog angles open to cushion weight load

Question 54

Artiodactyl foot lacks what

Answer 54

Frog

Question 55

What do the epidermal and dermal lamellae lack

Answer 55

Secondary lamellae

Question 56

In the Artiodactyl hoof what replaces the frog corium and is continuous with the sole corium

Answer 56

Digital pad corium, attaches to the 3rd phalanx, lateral cartilages and digital cushion

Question 57

Laminitis

Answer 57

Inflammatory process of the dermal lamellae that eventually leads to loss of lamellae interlocking and detachment of 3rd phalanx =