Integumentary System Lecture Notes #2 PDF

Integumentary System Lecture Notes #2 Monica N. Gonzales, DVM, MSVM CVM, PSAU Learning Objectives To identify the To know what is the different skin common appendages and its...

Integumentary System Lecture Notes #2 Monica N. Gonzales, DVM, MSVM CVM, PSAU Learning Objectives To identify the To know what is the different skin common appendages and its integument and its anatomy and functions functions Common integument Protective covering of the body Common integument Composed of skin, hair, claws, pads and mammary glands Skin (cutis) One of the largest organs of the body – 16% BW Continuous with the mucous membranes of the respiratory, digestive and urogenital tracts at the mucocutaneous junction Skin thickness of dogs Thickest – neck region Thinner - over the sternum Thinnest - ventral surface of the abdomen Functions of the skin: Protects the body from invasive microorganisms and noxious chemicals Prevents dessication and hydration Acts as a sensory organ Regulates temperature change Secretion of substances Excretion of substances Site of Vitamin D synthesis Reservoir of fats Reflects the general health condition of the animal Layers of the Skin Epidermis ▫ the most superficial layer ▫ non-vascular , composed of stratified squamous epithelium in varying thickness Dermis ▫ Lies immediately underneath the epidermis ▫ With vessels, nerves, and glands Hypodermis ▫ Subcutis or subcutaneous tissue ▫ Fats cells develop Layers of the Epidermis (Basement membrane) Stratum basale Stratum spinosum – prickle- cell layer Stratum granulosum – granular layer Stratum lucidum – clear layer Stratum corneum – horny layer Nasal skin – s.granulosum and s.lucidum are absent Dermis Strong, flexible connective tissue: your “hide” Cells: fibroblasts, macrophages, mast cells, WBCs Fiber types: collagen, elastic, reticular Rich supply of nerves and vessels Critical role in temperature regulation (the vessels) Hypodermis “Hypodermis” (Gk) = below the skin “Subcutaneous” (Latin) = below the skin Also called “superficial fascia” “fascia” (Latin) =band; in anatomy: sheet of connective tissue Fatty tissue which stores fat and anchors skin (areolar tissue and adipose cells) Different patterns of accumulation (male/female) Skin color     Derived from epidermis but extend into dermis Include  Hair and hair follicles Skin  Sebaceous (oil) glands appendages  Sweat (sudoiferous) glands  Nails  Mammary glands Hair and hair follicles: complex Derived from epidermis and dermis Everywhere but palms, soles, nipples, parts of genitalia *“arrector pili” is smooth muscle * Hair bulb: epithelial cells surrounding papilla Hair papilla is connective tissue________________ Functions of hair Warmth – less in man than other mammals Sense light touch of the skin Protection - scalp Parts Root imbedded in skin Shaft projecting above skin surface Make up of hair – hard keratin Three concentric layers Medulla (core) Cortex (surrounds medulla) Cuticle (single layers, overlapping)  Guard hairs are typically stiffer, harder, glossier, smoother, coarser, longer and/or thicker in diameter than the softer undercoat of a dog. The hair acts as an additional layer of insulation, a “topcoat,” if you will, to protect a dog from cold weather. It also helps prevent injuries to the dog’s skin, and, to a large extent, determines the dog’s appearance because of its unique coloring.  Denser - dorsal and lateral parts Thinner – abdomen, flanks and ears, and underside of the tail Hair Parts of the hair: Shaft (scapus pili) (pili) Root (radix pili) Vibrissae – enlarged hairs Superciliary hairs – enlarged hairs above the eye Vibrissae – enlarged hairs; these are tactile receptors located under the skin  Canine whiskers help a dog measure distance in the dark. Air currents, perceived by the vibrissae, allow a dog to obtain an idea about space size and object location in relation to the body. Purposes of The superciliary vibrissae (located vibrissae or above the eye), protect a dog’s eyes from dust and dirt in the air. “whiskers” A dog’s vibrissae perceive air currents, providing information about temperature to a dog’s brain. Classification of Haircoat of Dog Based on Length Normal coat ▫ Ex. Wolf, jackal, GS Short hair ▫ Ex. boxer  Long hair – wire hair, tight curly hair, and flat long hair ▫ Ex. Cocker spaniel, poodle Other classifications of hairs Straight hair Bristle hair Wavy bristle hair Bristled wavy hair Large wavy hair Fine wavy hair Muscles of the Skin Erector pili muscle ▫ Hair muscle ▫ Responsible for the erection of hairs in animals in response to cold, fear or anger (piloerection)  Cutaneous muscle / cutaneous trunci ▫ When contracted tend to move the skin and its associate structures ▫ Muscle that twitches the skin Glands of the Canine Skin Sweat glands ▫ Eccrine sweat glands secrete sweat directly onto the surface of the skin  located over almost the entire body, with higher # in the foot pads ▫ Apocrine sweat glands secrete fluid into the sac of hair follicle through which it eventually comes out on the skin  found in armpits, genital area, and around the nipples  Sebaceous glands ▫ Responsible for oily secretion Glands of ear canal ▫ Secretes cerumen Bartholin glands (bitch) two in number located in the constrictor muscles of the vestibule and secrete mucus most actively at estrus Each Bartholin gland opens in the lateral wall of the vestibule by a single duct  Glands of anal sac ▫ Lies in the 4 and 8 o’clock position of the anal canal ▫ Together with sebacious glands lead to formation of a viscous liquid or pasty material with a foul odor  Supracaudal gland / tail gland / violet gland ▫ Located at the dorsal aspect of the tail ▫ for intra-species signalling, scent marking, and contributes to the strong odor of foxes in particular Claws Functions: traction, defense, catching prey Parts: ▫ Sole ▫ Two walls ▫ Central dorsal ridge Digital pads Toughest region of the canine skin ▫ Rough surface of the pads are due to the presence of heavily keratinized conical papillae Mammary glands Cranial and caudal thoracic mammary glands Cranial and caudal abdominal mammary glands Inguinal mammary glands  Arterial supply of the thoracic and abdominal Blood supply of mammary glands – sternal branches of the mammary internal thoracic arteries Arterial supply of the inguinal mammary glands – glands external pudendal arteries Venous supply – cranial and caudal epigastric veins Cranial epigastric veins > internal thoracic vein > brachiocephalic veins > Cranial vena cava Caudal epigastric vein > external iliac vein > common iliac vein > caudal vena cava Nerve supply of mammary glands Cran. Thora. MG – 4th, 5th, 6th vent. cutaneous nerves Caud. Thora. MG – 6th & 7th vent. cutaneous nerves Abdominal & inguinal MG – inguinal nerve and the vent. superficial branches of the first 3 lumbar nerves