University:
Texas A&M University
Course:
BIOL 319 | Integrated Human Anatomy and Physiology I
Academic year:

2024
Views:

304

Pages:

70
Author:

Arielle Armstrong

Objectives To gain a greater appreciation of the diversity of functions of skin To recognize the different cell types and structures of the skin which make possible this functional diversity Functions of Skin: Functional Diversity of Skin • Protects against injury • Prevents desiccation and allows terrestrial (land-welling) existence • Maintenance of water balance • Excretes/secretes various substances • Thermoregulation • Receives stimuli − Temperature − Pain − Pressure • Basis of recognition and yields clues to one’s well being • Fat metabolism in the subcutaneous layer BINARY ORIGIN OF SKIN Thin skin Histo 31 EPIDERMIS – ECTODERM ECTODERM DERMIS MESODERM MESODERM HISTO31 111 Epidermis Skin Thin skin Dermis REGIONAL VARIATION OF THE EPIDERMIS • Thick skin - sole of foot (1.4 mm thick) • Thin skin - eyelid and most of body (0.07 to 0.12 mm) • Cornea of eye - transparent • Appendages - hair follicles, nails, glands 292 Tongue Histo 051 408 sole of foot Epidermis gives rise to numerous appendages Nails 209 Hair follicles 410 220 Breast (Mammary gland) Tarsal gland of eyelid Apocrine sweat Slide Histo66 recto-anal junction Tears Location of thin and thick skin and layers of skin Structures in skin Use your ATLAS for orientation Thin skin Thick skin Epidermis Thin skin Dermis Abdominal skin is the least specialized and most prototypic of skin in general (Slide 206). The dermis is dense irregular connective tissue. 206 Slide Histo 029: Thick Skin (ventral surface of finger) Epidermis ) Copyright McGraw-Hill Companies Dermis Hypodermis Adipocytes Thick Skin (ventral surface of finger) Epidermis Copyright McGraw-Hill Companies Papillary layer Dermal papillae Epidermal peg Slide 029 : Dermis Reticular layer Dermal sideof the epidermal – dermal interface Dermal papilla Capillaries In dermal papilla Circulation of Blood Through Skin A-V shunts facilitates rapid filling of venous plexus for skin cooling but also blushing capillary capillary artery A-V shunt Venous plexus Slide 029 : Thick Skin (ventral surface of finger) Meissner’s corpuscles in dermal papillae Epidermis Dermal papilla Epidermal peg Dermis Meissner’s corpuscle is a mechanoreceptor Epidermis nerve ending for sensitivity to light touch; you would find more on your fingers because they are more sensitive to touch than your elbow. Skin hand monkey 109 Eccrine sweat glands Adipocytes Hypodermis Pacinian corpuscles Papillary layer Dermal papilla Epidermal peg Fingertip, monkey - sweat glands and ducts among Pacinian corpuscles Eccrine sweat glands 105 Duct of sweat glands Pacinian corpuscle LAYERS OF THE EPIDERMIS: PALMS AND SOLES OF FEET STRATUM CORNEUM – KERATINIZED FLATTENED, DENUCLEATED, DEAD CELLS STRATUM GRANULOSUM – KERATOHYALIN GRANULES STRATUM SPINOSUM – TONOFIBRILS DESMOSOMES STRATUM BASALE – CONTINUAL RENEWAL OF EPIDERMIS Duct of sweat gland Slide 029 : Thick Skin (ventral surface of finger) cont. Keratohyalin granules Desmosomes Hemidesmosomes 1 2 3 2 3 4 5 4 1. Stratum corneum 2. Stratum lucidum 3. Stratum granulosum 4. Stratum spinosum 5. Stratum basale 5 Slide 029 : Thick Skin on finger cont. S. granulosum: flattened cells undergoing the terminal differentiation process of keratinization – forming . the skin’s barrier against water loss when sealed with contents of membrane coating granules. 1 Keratohyalin granules Desmosomes Hemidesmosomes Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale Slide 029 : Thick Skin on finger cont. The epidermis of thick skin is subject to continuous friction and pressure so the abundant desmosomes (and tonofibrils) withstand this and hold the cell layers together. Keratohyalin granules Desmosomes Hemidesmosomes 1 Epidermis Stratum spinosum Dermis Stratum basale STRATUM CORNEUM STRATUM GRANULOSUM STRATUM SPINOSUM STRATUM BASALE STRATUM BASALE STRATUM SPINOSUM SPINOSUM STRATUM STRATUM CORNEUM STRATUM GRANULOSUM STRATUM CORNEUM 31 EM 8g of skin Cells in EPIDERMIS The epidermis is classified as STRATIFIED SQUAMOUS epithelium – CELL TYPES INCLUDE: KERATINOCYTES - MAIN CELL TYPE – ECTODERM MELANOCYTES PIGMENTATION - NEURAL CREST LANGERHANS CELL IMMUNOLOGIC ROLE MERKEL CELLS ASSOCIATED WITH NERVE ENDINGS 111 107 CYTOCRINE SECRETION – PASS MELANIN GRANULES FROM MELANOCYTES TO KERATINOCYTES MELANIN-producing enzymes in MELANOCYTES Space of removed dermis EPIDERMIS 107 Slide 31: Thin Skin (scalp) Sun from NASA Stratum corneum Stratum granulosum Stratum spinosum Stratum basale Melanin capping of nuclei Thin Skin 31 (scalp) Sun from NASA Stratum corneum Stratum granulosum Stratum spinosum 4 Stratum basale Melanin capping of nuclei MELANOCYTE - PIGMENT SYNTHESIS FRECKLES - MELANIN DISTRIBUTED IN PATCHES MELANOCYTE – disease states ALBINISM - FAILURE TO PRODUCE MELANIN MALIGNANT MELANOMAS - CANCER ADDISON’S DISEASE - PIGMENT DEPOSITION IN SKIN DUE TO ADRENOCORTICAL INSUFFICIENCY Epidermal – dermal interface finger pad Epidermis Dermis Epidermal – dermal interface creates unique epidermal ridges 209 arrector pili muscle vascularized dermal papillae Pilosebaceous unit sebaceous glands Swear glands Slide 31: Thin Skin (scalp) Arrector pili muscle Copyright McGraw-Hill Companies Hair follicle location Sebaceous glands Skin, scalp 209 Human Skin, scalp 108 Skin, scalp Arrector pili muscle Mode of secretion of the sebaceous glands is holocrine where by the sebum is released when cells burst. sebaceous glands Eccrine sweat glands Eccrine sweat glands 105 epidermis stratum corneum 408 Openings of ducts of sweat glands Slide 66: Recto-anal junction Eccrine sweat glands Sebaceous gland Hair follicle Myoepithelium 66 Stratified squamous epithelium of anal wall Simple columnar epithelium of rectum with goblet cells Slide 66: Recto-anal junction hair Sebaceous gland Apocrine sweat gland Mucocutaneous Junctions Lips, Nares, Eyelids, Vulva or Prepuce Anal Canal MECHANISM FOR RELEASE OF SECRETORY PRODUCTS MEROCRINE SECRETION – EXOCYTOSIS W/O LOSS OF SURFACE MEMBRANE (sweat, casein in milk) APOCRINE SECRETION – LOSS OF PART OF APICAL CYTOPLASM AND SOME PLASMA MEMBRANE (milk fat) HOLOCRINE SECRETION – RELEASE OF WHOLE cell (Sebaceous gland) MEROCRINE 66 APOCRINE HOLOCRINE OTHER GLANDS OF EPIDERMAL ORIGIN SWEAT GLANDS – ECCRINE - COMMON SWEAT GLAND LOCAL COOLING – APOCRINE AXILLARY REGION FUNCTION IN ANIMALS SWEAT GLANDS secretions Slide 29: Thick Skin (ventral surface of finger) Myoepithelial cells are eosinophilic because of the presence of muscle contractile proteins, which contract to expel sweat when needed. Ducts of eccrine sweat glands with stratified cuboidal epithelium Myoepithelial cells Eccrine sweat glands SWEAT GLAND Mammary gland -myoepithelial cells are responsible for milk ejection from alveoli during nursing. THREE TYPES OF GRANULES in skin MELANIN – SKIN PIGMENT – PRODUCED BY MELANOCYTES AND PASSED BY CYTOCRINE SECRETION TO KERATINOCYTES MEMBRANE COATING GRANULES (LAMELLATED GRANULES) – WATER PROOFING FUNCTION – PRODUCED BY KERATINOCYTES KERATINOHYALIN GRANULES • PRODUCED BY KERATINOCYTES THREE TYPES OF GRANULES IN Skin MEMBRANE COATING GRANULES (LAMELLATED GRANULES) – Small, ovoid structures from the Golgi containing various lipids and they undergo exocytosis to produce a lipid-rich impermeable layer around the cells of the s. granulosum – water proofing. THREE TYPES OF GRANULES in skin KERATINOHYALIN GRANULES – CHEMICAL NATURE NOT CLEARLY ESTABLISHED – RICH IN HISTODINE FORMS – MATRIX OF CELLS IN STRATUM CORNEUM, STABILITY DUE TO DISULFIDE BONDS – ABSENT IN HAIR AND NAILS Regeneration of epidermis Dermis Elastic fibers - Network between collagen bundles muscle Smooth muscle - loose plexus in reticular layer in areolae, penis, perineum, and scrotum Epidermis Smooth muscle Ref code #9 Dermis Muscle Smooth muscle –hair follicles, nipple of human breast Skeletal muscle – terminated in the dermis • Facial expression Also, hair follicles, glands, blood vessels, nerves, and nerve endings abound 108 Sebaceous gland 411 Dermis Muscle Skeletal muscle terminated in the dermis • Facial expression KERATINIZED STRATIFIED SQUAMOUS [EPITHELIUM] #5 NONKERATINIZED STRATIFIED SQUAMOUS [EPITHELIUM] Slide #83 (SP-1-79). Skin of lip, sheep. NONKERATINIZED STRATIFIED SQUAMOUS [EPITHELIUM] oral cavity skin KERATINIZED STRATIFIED SQUAMOUS [EPITHELIUM] skin adnexa (i.e., hair/hair follicles, sebaceous & sweat glands, arrector pili muscles 136 Tongue, monkey Epidermal and Dermal – nerve Interfaces Histo 029 109 Clinical Correlation Albinism can be caused by a hereditary defect in tyrosinase activity or the inability of cells to take up tyrosine. Tyrosine amino acid figure chemistry.about.com. Patient with albinism would be more at risk for the development of basal and squamous cell carcinomas as albinism produces skin hypopigmentation so fewer melanin granules to protect nuclear DNA from the ionizing, mutagenic effects of UV radiation. Albino peacock http://www.duskyswondersite.com/animals/albino-animals/ In summary Questions Integumentary System 1. Which layer of the epidermis has meiotic activity? a. stratum basale b. stratum spinosum c. stratum granulosum d. stratum corneum e. none of the above 2. Which of the following skin granule - function(s) match(es)? a. melanin - skin pigment b. membrane coating granules - waterproofing c. keratinohyalin granules - forms junctions between adjacent cells d. a and b e. a, b, and c 3. Which function(s) of skin involve(s) granules: a. protection against ultraviolet light b. protection against mechanical injury as granules form matrix of cells in stratum corneum c. protection against desiccation d. a and b e. a, b, and c 4. The dermis: a. has muscle (smooth and/or skeletal) b. has elastic fibers that are reduced with age c. has a reticular layer that interacts with/has direct contact with the epidermis d. a and b e. a, b, and c

Thick Skin Histology

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