A&P-integument

Anatomy & Physiology: Integumentary system

Integument Overview

• Components:

  • Skin (cutaneous epithelium)

    • Epidermis

    • Dermis

    • Hypodermis

  • Accessory Organs:

    • Glands:

      • Sweat

      • Sebaceous

      • Mammary

    • Dermal Structures:

      • Papillae

Protective Structures

• Accessory Organs:

  • Hair

  • Feathers

  • Claws

  • Hooves

  • Beaks

  • Scales

  • Horns and Antlers

Functions of the Skin

• Protection:

  • Shields against physical trauma

  • Acts as a barrier against pathogen invasion:

    • Physical and chemical

  • Maintains hydration:

    • Prevents loss and excessive intake

    • Blocks harmful radiation

  • Pigmentation: Provides color and protects from UV rays

• Sensation:

  • Serves as an external sensory monitor:

    • Contains nerve endings for temperature, pressure, and touch

    • Involves nociceptors for detecting pain

• Secretion:

  • Produces substances such as:

    • Sebum

    • Sweat

    • Pheromones

• Vitamin D Production

• Thermoregulation:

  • Regulating body temperature through sweating and blood flow to the skin

• Communication:

  • Visual signals through skin and hairs

• Attachment and Storage:

  • Stores fat in the hypodermis

Skin Structure

• Largest Organ: Functions as the external surface of the body

• Keratinization: The outer layer consists of dead, keratinized cells

• Variability: Skin thickness varies across different body areas (e.g., nose, pads, abdomen, scrotum)

Epidermis

• Characteristics:

  • Avascular layer of stratified squamous epithelium

• Structural Layers:

  • Stratum Basale:

    • Site of germinal cell activity, contains melanocytes and Merkel discs

  • Stratum Spinosum:

    • Contains desmosomes and Langerhans cells

  • Stratum Granulosum:

    • Contains keratohyaline and contributes to waterproofing

  • Stratum Lucidum:

    • Present in thick skin, provides translucency

  • Stratum Corneum:

    • Thickest layer of dead cells that are shed regularly

Dermis

• Thickest Layer: Provides strength and elasticity

• Layers:

  • Papillary Layer:

    • Interdigitates with the epidermis, contains Meissner's corpuscles and blood vessels

  • Reticular Layer:

    • Contains tough collagen fibers, fibroblasts, macrophages, and sweat glands

Hypodermis

• Subcutaneous Layer:

  • Composed of areolar and elastic connective tissue

  • Functions as fat storage, contains blood vessels and nerves

  • Pacinian Corpuscles: Detects pressure and vibration

Specialized Skin Structures

• Nasal Planum: Thick, pigmented skin with specialized melanocytes

• Foot Pads: Provides physical and thermal protection; various types for different foot areas including digital and stopper pads

Specialized Skin in Equines

• Ergot and Chestnuts: Remnants of pad structures, located on the lower limbs

Accessory Glands

• Sweat Glands: Have apocrine and eccrine types, with variability among species

• Sebaceous Glands: Produce oily secretions; modifications include tail glands and ceruminous glands

Hair Structure and Development

• Follicle Development:

  • Hair cone and bulb formed from keratinized cells

  • Dermal papilla provides blood and nerve supply

• Types of Hair:

  • Guard (primary), wool (secondary), and tactile (vibrissae) hairs

• Growth Cycles:

  • Anagen: Growth phase

  • Catagen: Transition phase

  • Telogen: Resting phase

  • Factors affecting cycles include temperature, light, and hormonal changes

Claws and Hooves

• Anatomy:

  • Claws consist of ungual process and corium

  • Hooves have similar structure:

    • Coffin bone, sensitive corium, and wall structures

  • Frog: Elastic component aiding in circulation; ensures no valves are needed for blood return during movement

Horns and Antlers

• Horns:

  • Continuous growth, composed of keratinized epithelial tissue, varies in shape and size among species

• Antlers:

  • Shed annually, growth covered by vascularized velvet, undergo endochondral ossification