Integumentary System - Part Three Study Notes

Integumentary System - Part Three Notes

Introduction

• Introduction by the speaker (unidentified) along with "Fig", a cat that appears in the presentation.

• Continuation from part two of the integumentary system lecture.

Claws and Dewclaws

• Claws:

  • Definition: Hard outer coverings of the distal digits.

  • Characteristics: Non-retractable in most species (retractable in most cats).

  • Functions:

  • Provide good traction

  • Tools for defense

  • Assist in catching prey

  • Reference to an exercise in the lab manual to identify different parts of claws.

• Dewclaws:

  • Definition: Remnants of digits that have regressed through evolution.

  • In dogs, the dewclaws correspond to the first digit; however, actual bones are only present in dewclaws of the forelimbs.

  • In cattle, pigs, and sheep:

  • Medial and lateral dewclaws are the second and fifth digits, respectively.

  • Only pigs have dewclaws with bones (contain both metacarpal and phalangeal bones).

  • Procedure: Dewclaw amputation requires the removal of the entire third phalanx.

  • Oneyctomy:

  • Refers to the surgical removal of a claw (the entire tip of the digit).

  • Comparison to cutting off the fingertip in humans.

Hooves

• Hooves (Ungula):

  • Definition: Horny outer covering of digits in some animals; one hoof covers each digit.

  • Weight-bearing capabilities vary among species.

  • Hooves rest on tissue called the corium.

  • Structure:

  • Inner layer: Modified dermis (corium).

  • Outer layer: Modified epithelial (hoof).

  • Ruminants have four hooves per foot; originally five toes exist in their evolutionary ancestors.

  • The thumb (first digit) regressed, while the index (second) and pinky (fifth) digits are now dewclaws, behind the weight-bearing hooves.

  • Horse Anatomy:

  • Horses walk only on one digit per foot; the middle finger (third digit) equivalent.

  • The corium provides nourishment to the developing cells of the hoof through blood vessels.

  • Process of keratinization:

    • Cells originate from the stratum germinatum and move upwards through layers (stratum spinosum, stratum lucidum, stratum corneum) until they are fully keratinized and dead.

  • Laminae:

  • Structure composed of primary and secondary lamina located between the hoof wall and third phalanx (coffin bone).

  • Nutritional support to the stratum internum.

  • Laminitis: Inflammation of the laminar corium causing severe pain, often resulting from malnutrition.

  • Corium Types:

  • Perioplic Corium: Located on the perioplic sulcus; nourishes the periapole.

  • Coronary Corium: Located in the coronary sulcus; nourishes the stratum external and stratum medium.

  • Sole Corium: Located superior to the sole; nourishes the sole area.

  • Frog Corium: Located above the frog area; supplies nutrients to the frog.

  • Skeletal Structure:

  • Includes the distal part of the second phalanx, distal sesamoid bone (navicular), entire third phalanx (coffin bone).

  • Structure composed of:

    • Distal Phalanx (coffin bone)

    • Short Pastern Bone (Middle Phalanx)

    • Long Pastern Bone (Proximal Phalanx)

  • Hoof interdigitations (laminae) increase the contact area between hoof wall and corium, forming strong attachment.

Comparative Anatomy

• Comparison between bones of human feet and that of horses, showcasing similarities like the cannon bone, long pastern, etc.

• Reference to essential knowledge of the equine hoof, which is relevant for veterinary technicians.

• Importance of understanding the hoof due to various conditions that can affect horses.

Hoof Structure (Key Components)

• Hoof Wall (Number 5):

  • Convex external structure visible from anterior, lateral, and medial views.

  • Divided into three regions: toe, quarters, and heels.

• Sole (Number 3):

  • Concave structure filling space between wall and bars.

  • Angle surrounds the bars.

  • Avascular and lacks innervation in outer layer; nutrient flow originates deeper in corium.

  • White line formed at junction of the sole and hoof wall (Number 4).

• Frog (Number 1):

  • Triangular structure located between the heels on the underside of the hoof.

  • Divided by central sulcus and separated from bars by collateral sulcus.

  • Digital cushion underneath providing support; sensitive to external stimuli.

Horns

• Definition of Horns:

  • Masses of horny keratin that grow continuously and are not sex-specific (myth that only bulls have horns).

  • Structural composition similar to hair and epidermal in origin.

  • Emerge from frontal bone processes and differ in shape across species.

• Horn Structure:

  • Generally hollow in adults, connected to the frontal sinus.

  • Apex of the horn stronger and denser than the base.

• Dehorning:

  • Common practice involves removal of horn buds before significant growth, often via cauterization to prevent regrowth.

  • Breeds developed to be horn-free are referred to as pulled breeds.

Antlers

• Definition of Antlers:

  • Sex specific structure that is shed annually, primarily associated with males in the Cervidae family (e.g., deer, moose).

  • Velvet skin nourishes the antler during growth, and subsequent processes lead to shedding.

• Significance:

  • Used as a display of strength during mating season.

  • Growth correlated with calcium in diet.

Key Comparisons Between Horns and Antlers

• Clarification of structural and growth differences between the two.

Conclusion

• Encouragement to familiarize with key terms located in the lab manual and textbook for upcoming assessments.

• Availability of the PowerPoint for further study.

• Invitation for questions and reminders for further learning and engagement with lab manuals.

• Farewell from the speaker and Fig.