Podcast
Questions and Answers
Which of the following is NOT part of the common integument?
Which of the following is NOT part of the common integument?
The skin is the largest organ in the animal's body.
The skin is the largest organ in the animal's body.
False
What is the name for the layer of skin that lies immediately underneath the epidermis?
What is the name for the layer of skin that lies immediately underneath the epidermis?
Dermis
The outermost layer of the skin is called the ______
The outermost layer of the skin is called the ______
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Match the following skin layers with their descriptions:
Match the following skin layers with their descriptions:
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Which of the following is NOT a function of the skin?
Which of the following is NOT a function of the skin?
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What is the name of the layer of fat that lies beneath the skin?
What is the name of the layer of fat that lies beneath the skin?
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The epidermis is composed of connective tissue.
The epidermis is composed of connective tissue.
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Which of the following is a type of skin pigment?
Which of the following is a type of skin pigment?
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What is the common name for vibrissae?
What is the common name for vibrissae?
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Guard hairs are typically softer and finer than the undercoat.
Guard hairs are typically softer and finer than the undercoat.
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Which of the following is NOT a type of hair found in dogs?
Which of the following is NOT a type of hair found in dogs?
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What is the name of the muscle that is responsible for raising the hair on an animal's body?
What is the name of the muscle that is responsible for raising the hair on an animal's body?
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Eccrine sweat glands are found primarily in the foot pads of dogs.
Eccrine sweat glands are found primarily in the foot pads of dogs.
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Which of the following is NOT a function of the anal sacs?
Which of the following is NOT a function of the anal sacs?
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What is the name of the gland found on the dorsal aspect of a dog's tail?
What is the name of the gland found on the dorsal aspect of a dog's tail?
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Claws are primarily used for grooming and hygiene.
Claws are primarily used for grooming and hygiene.
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Which part of the claw provides the central ridge?
Which part of the claw provides the central ridge?
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What is the name of the tough, keratinized, conical projections found on the pads of a dog's foot?
What is the name of the tough, keratinized, conical projections found on the pads of a dog's foot?
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Mammary glands are only found in female dogs.
Mammary glands are only found in female dogs.
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Study Notes
Integumentary System Lecture Notes
- The integument is the protective covering of the body, composed of skin, hair, claws, pads, and mammary glands.
- Learning objectives include understanding the common integument and its functions, and identifying different skin appendages, their anatomy, and functions.
- The skin (cutis) is a major organ, comprising 16% of body weight.
- The skin is continuous with mucous membranes in the respiratory, digestive, and urogenital tracts, uniting at the mucocutaneous junction.
- Skin thickness varies, thickest in the neck region, thinner over the sternum, and thinnest on the abdominal ventral surface.
- Skin functions include protecting against microorganisms and noxious chemicals, preventing dehydration, acting as a sensory organ, regulating temperature, secreting substances, excreting substances, synthesizing vitamin D, and acting as a fat reservoir. It also reflects the overall health condition of the animal.
Layers of the Skin
- Epidermis: The outermost, non-vascular layer composed of stratified squamous epithelium. It varies in thickness.
- Dermis: Lies beneath the epidermis, containing vessels, nerves, and glands, and offering structural support.
- Hypodermis: Also known as subcutis or subcutaneous tissue, it's composed of fat cells.
Layers of the Epidermis
- Stratum basale (basement membrane): Deepest layer.
- Stratum spinosum (prickle-cell layer): Located above the basale.
- Stratum granulosum (granular layer): Above the spinosum.
- Stratum lucidum (clear layer): Present in thick skin regions.
- Stratum corneum (horny layer): Outermost layer. Nasal skin lacks the stratum granulosum and stratum lucidum.
Dermis
- Composed of strong, flexible connective tissue (the "hide").
- Contains cells like fibroblasts, macrophages, mast cells, and white blood cells (WBCs).
- Contains collagen, elastic, and reticular fibers.
- Houses a rich supply of nerves and vessels, which play a crucial role in temperature regulation.
Hypodermis
- Also called superficial fascia, it's a layer of subcutaneous tissue.
- This layer stores fat and anchors the skin (primarily areolar tissue and adipose cells).
- Fat accumulation patterns differ between males and females.
Skin Color
- Pigments include melanin (most important), carotene (from carrots and yellow vegetables), and hemoglobin (contributing to the pink color of light skin).
Skin Appendages
- Derived from the epidermis but extend into the dermis.
- Include hair and hair follicles, sebaceous glands, sweat glands, nails, and mammary glands.
Hair and Hair Follicles
- Present everywhere except palms, soles, and parts of genitalia.
- Hair follicles include an "arrector pili" (smooth muscle), epithelial cells, and the hair bulb. The hair shaft comprises cuticle, cortex, and medulla.
- Hair is composed of hard keratin.
- Layers: medulla (core), cortex (surrounds medulla), cuticle (single layers, overlapping).
Functions of Hair
- Provides warmth (less so in humans compared to other mammals).
- Acts as a sensory organ for perceiving light touch.
- Protects from the environment, notably the scalp.
Guard Hairs
- Typically stiffer, harder, glossier, smoother, coarser, longer, and/or thicker in diameter than the undercoat.
- Serve as an additional layer of insulation (topcoat) protecting from cold weather and physical injury.
- Contribute significantly to the dog's appearance due to unique coloration.
Hair (Pili)
- Vary in density across different body regions (denser on dorsal and lateral parts, thinner on the abdomen, flanks, ears, and underside of the tail).
- Components: shaft (scapus pili), root (radix pili).
- Vibrissae - enlarged hairs acting as tactile receptors located beneath the skin. Superciliary hairs – above the eyes act as defense against environmental irritants.
- Whiskers have a crucial functional role, particularly in locating and navigating their environment in the dark.
Muscle of the Skin
- Erector pili muscle: Contraction causes hairs to stand on end, helping in temperature regulation, and responding to stimuli like fear and cold. Also known as piloerection.
- Cutaneous Muscle (cutaneous trunci): Contraction causes the skin to twitch.
Glands of the Canine Skin
- Sweat glands (Eccrine): Secrete sweat directly onto the skin surface all over the body, with a higher concentration in paw pads.
- Sweat glands (Apocrine): Secrete fluid into hair follicles and exit onto the skin; abundant in armpits, genital areas, and around nipples.
- Sebaceous glands: Responsible for oily secretions throughout the body impacting coat and skin health.
- Glands of the ear canal: Responsible for secreting cerumen.
- Bartholin glands (in bitches): Located in the vestibule, secrete mucus mainly during estrus. Two in number per individual.
- Anal Sac Glands: Located in the anal canal (at 4 and 8 o'clock), secreting a viscous liquid that, with sebaceous secretions, can have a foul odor.
- Supracaudal Gland: Located on the dorsal aspect of the tail, responsible for intraspecies signaling, marking, and emitting a pronounced scent.
Claws
- Functions: traction, defense, catching prey.
- Parts: sole, two walls, central dorsal ridge.
Digital Pads
- The toughest area of the canine skin, with a rough surface due to heavily keratinized conical papillae.
Mammary Glands
- Types: cranial and caudal thoracic, cranial and caudal abdominal, inguinal.
- Locations vary across the body.
Blood Supply of Mammary Glands
- Arterial supply from sternal branches of internal thoracic and external pudendal arteries.
- Venous supply involves cranial and caudal epigastric veins, drainage into brachiocephalic, common iliac, and caudal vena cava veins.
Nerve Supply of Mammary Glands
- Cranial thoracic mammary glands receive innervation from cranial 4th, 5th, and 6th ventral cutaneous nerves.
- Caudal thoracic mammary glands receive innervation from cranial 6th and 7th ventral cutaneous nerves.
- Inguinal mammary glands receive innervation from inguinal nerves and ventral branches of lumbar nerves.
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