Chapter 5

PHYSIOLOGY OF THE SKIN

4/7/20111INTRODUCTIONOrgan terbesar di tubuh

Menutupi area permukaan tubuh hingga 1,6 m2Kira-kira 16% dari total berat badan dewasa

4/7/20112FUNGSI ???4/7/20113Fungsi Proteksi

Melindungi bagian dalam tubuh manusia terhadapgangguan fisik&mekanik : tekanan, gesekan, tarikan, panas/dinginlemak subkutis, tebalnya lapisan kulit, & serabut penunjang gangguan sinar UV melaningangguan jamur, bakteri/virus kelenjar2 kulit yang mempunyai pH 5,0 - 6,5

4/7/20114Fungsi Absorpsi

Kulit yang sehat tidak mudah menyerap air, larutan.

Kemampuan absorpsi kulit dipengaruhi : tebal tipisnya kulit, hidrasi, kelembaban udara, metabolisme dan jenis vehikulum zat yang menempel di kulit.

4/7/20115Penyerapan dapat melalui celah antar sel, saluran kelenjar atau saluran keluar rambut.

4/7/20116Fungsi Ekskresi

Kelenjar kulit mengeluarkan zat yang tidak berguna/sisa metabolisme tubuh : NaCl, urea, amonia, dan sedikit lemak.

Kelenjar lemak pada fetus, atas pengaruh hormon androgen dari ibunya, akan menghasilkan sebum untuk melindungi kulitnya terhadap cairan amnion yang pada waktu lahir disebut vernix caseosa. 4/7/20117Sebum yg diproduksi kelenjar lemak melindungi kulit : meminyaki kulit & menahan penguapan berlebihan, kulit tidak kering.

Produk kelenjar lemak & keringat, di permukaan kulit membentuk keasaman kulit pada pH 5 - 6,5.

4/7/20118Penguapan air dari dalam tubuh dapat secara difusi melalui sel-sel epidermis, tetapi karena sel epidermis baik fungsi sawarnya, maka kehilangan air melalui sel epidermis (transepidermal water loss) dapat dicegah agar tidak melebihi kebutuhan tubuh.

4/7/20119Fungsi Pengindra (Sensori)

Kulit mengandung ujung-ujung saraf sensorik di dermis dan subkutis. Badan Ruffini yang terletak di dermis, menerima rangsangan dingin rangsangan panas diperankan oleh badan Krausse. Badan taktil Meissner yang terletak di papil dermis menerima rangsang rabaan & badan Merkel-Renvier di epidermis. 4/7/201110Fungsi Termoregulasi

Dengan cara mengeluarkan keringat dan mengkontraksikan otot dinding pembuluh darah kulit.

4/7/201111Fungsi Pembentukan Pigmen (Melanogenesis)

Sel pembentuk pigmen kulit (melanosit) terletak di lapisan basal epidermis

Pajanan sinar matahari mempengaruhi produksi melanin. Bila pajanan bertambah, produksi melanin akan meningkat4/7/201112Fungsi Keratinisasi

Untuk menggantikan sel kulit mati, shg kulit dapat melakukan rehabilitasi dan menjalankan fungsinya dengan baik secara terus menerus

4/7/201113The Architecture of the SkinTdd 3 lapisan :

EpidermisDermisSubcutaneous tissues

4/7/201114Stratum basale (Basal cell layer)Lapisan selapis sel cuboidal/columnar Tdp Stem cells, melanocytes, dan Merkel cells

Stratum spinosum 8-10 lapisan sel bentuk poligonalTdp sel Langerhans

Epidermal Cell Layers4/7/201115Stratum granulosum3-5 layers of flattened, beginning breakdown of nucleus, cell death initiatedStratum lucidumonly in thick skin (palms, feet)3-5 layers of clear, flat dead cells with keratinStratum corneum 20-30 layers of flattened, dead, keratin-filled cellscontinuously shed and replaced3-4 weeks for each cell to form and to move from the stratum basale to the surface

Epidermal Cell Layers4/7/201116

The EpidermisStratified Squamous Epithelium4 cell typesKeratinocytes - 95%filled with keratin (protein)waterproof barrierMelanocytes produce melanin (pigment)Langerhans cellsphagocytes (from immune system)easily damaged by UV lightMerkel cellsin deepest layer of hairless skinsensory transduction - touch4/7/201117KeratinocytesMemproduksi keratin yg mengalami diferensiasi dan migrasi ke lapisan atas setelah dewasa (keratinization)

Turut berperan dalam pertahanan kulit

Mensekresi sitokin billa terjadi cidera sel kulit sehingga dapat menginduksi respon inflamasi4/7/201118Melanocytes and melanin synthesisMelanocytes dpt ditemukan di lapisan sel basal dan matrix

1000-1500 melanocytes ditemukan tiap mm2 kulit

Melanin diproduksi dr aa tyrosine di dalam melanosom

4/7/201119Biosynthesis of melanin

4/7/201120Functions of melaninMelindungi kulit dr sinar UV dan mencegah cidera sinar matahari ke kulit

Memberikan warna gelap pada kulit. Jumlahnya yang rendah berhubungan dengan risiko meningkatnya insidensi Malignancy

Dapat mengabsorbsi enzim aktif yg berbahaya, metal dan drugs

4/7/201121Langerhans cellIs a bone marrow-derived dendritic cell specific to stratified squamous epithelia

Frequently seen isolated in the middle and suprabasal cell layers

400/mm2 1000/mm2

Involved in cell-mediated hypersensitivity, antigen processing and recognition, stimulation of immune-competent cells, and graft rejection.

4/7/201122DermisThe structure beneath the epidermis.It consists of three layers :Papillary layerSubpapillary layerReticular layer

4/7/201123

Dermis - StructurePapillary region (layer) - outer layer - 20%Areolar connective tissue, elastic fibersDermal papillae mound-like projections to increase the surface area for nutrition from capillariesSome papillae contain Meissner's corpuscles (for light touch)4/7/201124

Dermis StructureReticular region - 80%Dense, irregular connective tissue Collagen, elastic fibers in a network surrounding the various cellsFibers give strength, elasticity, extensibility4/7/201125Elastic fibers

4/7/201126Cellular componentsFibroblast

Differentiates from mesenchymal cell

Produces collagen fibers, elastic fibers, glycosaminoglycans

4/7/201127Histiocyte

A kind of macrophage

In the dermis and subcutaneous tissues

Degrades&phagocytoses mainly foreign substances

4/7/201128Mast cell

Found in the dermis around capillaries & in the periphery of subcutaneous tissues

Produces & maintain various vasodilatory & hyperlucent chemical mediators

Multiple mast cell granules distributed in cytoplasm

4/7/201129Plasma cell

Is a differentiated B cell that has been stimulated by an antigen

Produces antibodies & involved in humoral immunity

The diameter is twice as large as a leukocyte

4/7/201130Vascular channels and nervesBlood vessels

Arteriovenous anastomosis controls the peripheral blood flow and is involved in body temperature regulation

Endothelial cells, pericytes, & multilayered basement membrane(lamina densa) are found in capillaries

4/7/201131Lymphatic vessel

Are distributed around the subpapillary layer, extend through postcapillary lymph vessels to dermal& subcutaneous lymph vessels

4/7/201132Nervous systemThe nerve fibers :Myelinated nerve fibersNon-myelinated nerve fibersThe sensory nerves transmit tactile, pressure, pain&temperature sensationThe autonomic nerves control the blood vessels, sweat glands & other appendages

4/7/201133Sensory nerveFree nerve endingAre distributed in the dermal upper & papillary layerNonmyelinated nerves transmit pain sensationsEnd corpuscleMeissner end corpuscle : in the dermal papillae perceiving tactile & light pressure sensationsPacinian corpuscle :In the dermal deep layer & subcutaneous tissuePerceiving pain and pressure sensation

4/7/201134

4/7/201135Autonomic nervesDistributed in the sweat glands, arrector pili muscles, blood vessels & glomus apparatuses control the functions of these organs

The cholinergic nonmyelinated sympathetic nerves are distributed in the eccrine sweat glands

The adrenergic symphathetic nerves are distributed in the arrector pili muscles and blood vessels4/7/201136Subcutaneous fat tissueThe layer between the dermis and the fasciaAct to preserve neural fat, cushion against external physical pressure, retain moisture and generate heatIs largely composed of fat cellsAssembled fat cells separated by connective fibroid fat septum (fat lobules)

4/7/201137AppendagesHair apparatus

Protecting the scalp from external forces and lightModerating heat in the headFound throughout the skin except lips on the mouth

4/7/201138Hair follicle

Is double bounded with two layers:Epithelial components; are inner & outer root sheathsConnective tissue component; is called connective tissue sheath

4/7/201139

4/7/201140Arrector pili muscle

A smooth muscle bundle between ORS and dermal upper layer.Cause hair stand verticallyControlled by adrenergic sympathetic nervesContracted by cold stress & emotional stress(fear & surprise)

4/7/20114142OIL PRODUCTIONOil is produced in the sebaceous gland , production is stimulated by hormones

Oil flows into the hair follicle then into the skin surface42Sebaceous (Oil) GlandsConnected to hair follicles; located in the dermis

Most secrete directly into follicles; some directly onto the skin

Gland shape differs depending on location

Holocrine gland

The Fx of sebum (oil)keeps hair from dryingprevents water evaporation from skinkeeps skin soft, suppleinhibits growth of many bacteria

4/7/201143Sudoriferous (Sweat) GlandsSweat: a plasma filtrate consisting of water, salts, urea, uric acid, amino acids, ammonia, sugar, lactic acid, ascorbic acid, and pheromones

pH between 4 and 6

Salty and acidic solution inhibits most bacterial growth

Maintain body temperature, but insignificant for waste removal

Two types: Eccrine sweat glandsApocrine sweat glands

4/7/201144Eccrine Sweat Glands

4/7/201145Apocrine Sweat GlandsSecretory portion is located in the dermis or the subcutaneous region; secrete into hair follicles

Secrete more during emotional stress, sexual arousal

http://faculty.une.edu/com/abell/histo/histolab3g.htm4/7/201146Modified Sudoriferous (Sweat) GlandsTwo types of modified sweat glands

Ceruminous glands protect against ectoparasites (bugs)Produce a bitter waxy secretion (cerumen)Open into the external auditory meatus (ear canal) or into local sebaceous glands

Mammary glands highly specialized for milk productionHormonally regulated by estrogens, prolactin, and oxytocin4/7/201147THANX YOU4/7/201148