Lecture 2 Anatomy PDF

HUMAN CELL & SKIN BMS10103: ANATOMY FOR HEALTH PROFESSIONAL Dr. Norhazilah Muhamad Department of Anatomy & Physiology Faculty of Medicine Strictly for educational purposes only  LEARNING OUTCOMES Explain the structure of cell membrane and nucleus....

HUMAN CELL & SKIN BMS10103: ANATOMY FOR HEALTH PROFESSIONAL Dr. Norhazilah Muhamad Department of Anatomy & Physiology Faculty of Medicine Strictly for educational purposes only  LEARNING OUTCOMES Explain the structure of cell membrane and nucleus. List all the organelles of a cell and their function. Describe the different layers of the skin. State the types of skin and their functions. Discuss the skin appendages and sensory nerve endings.  CELL The smallest structural and functional unit of an organism. Can only be observed under a microscope  microscopic. 2 types: 3  STRUCTURE OF CELL NUCLEUS It is bound by cell membrane (plasma membrane) within which is enclosed the protoplasm. PLASMA MEMBRANE Protoplasm consists of  Nucleus - inner dense part  Cytoplasm - outer less dense part CYTOPLASM Nucleus is separated from the cytoplasm by the nuclear membrane  Cytoplasm consists of a fluid base  cytosol o which contains a number of organelles ORGANELLES  a specialized subunit that has specific function. 5  CELL MEMBRANE Assignment:  Explain and draw the structure of cell membrane. 6  NUCLEUS  Nucleus is a membrane-bound organelle within a cell that contains the chromosomes.  Function:  controls and regulates the activities of the cell  carries the genes, structures that contain the hereditary information  Consists of:  Nuclear envelope/membrane  Neucleoplasm  Nucleolus  Chromosome  COMPONENT OF NUCLEUS  NUCLEAR ENVELOPE/MEMBRANE A double-layered system that encloses the elements of the nucleus. Its outer layer is combined with the endoplasmic reticulum. A liquid-filled space or perinuclear space is present between the two layers of a It is made up of lipoproteins, nuclear membrane. perinuclear space, pores, annuli material, an inner dense lamella.  COMPONENT OF NUCLEUS  NUCLEOPLASM/ NUCLEAR SAP The clear homogeneous ground substance of a cell nucleus. It is composed mainly of the nuclear proteins but it also contains other inorganic and organic substances such as nucleic acids, proteins, enzymes and minerals.  NUCLEAR PORE Fx: contains a number of enzymes  a protein-lined channel in the which help in the synthesis and nuclear envelope that regulates the functioning of DNA and RNA transportation of molecules between (genetic material). the nucleus and the cytoplasm.  ORGANELLE & ITS FUNCTION 10  SKIN  Largest and heaviest single organ in the body.  15-20% of total body weight  Composed of 2 layers:  Epidermis - epithelial layer of Ectodermal origin.  Dermis - Connective tissue of Mesodermal origin.  Based on epidermal thickness skin:  Thick skin – glaborous/smooth, non hairy  Thin skin – hairy skin  INTEGUMENTARY SYSTEM the largest organ of the body Composed of: forms a physical barrier between  Skin the external environment and the  Hair internal environment  Nails *serves to protect and maintain.  Glands  Nerves SKIN: LAYERS SKIN: LAYERS  Epidermis (outermost layer)  Provides waterproof barrier & creates skin tone.  Derivatives of epidermis are hair, nail, sebaceous and sweat glands.  Presence of Dermal papillae Projection of dermis interdigitate with epidermis.  Dermis  Composed of dense connective tissue which imparts mechanical support, strength and thickness to the skin.  Hypodermis (superficial fascia)***  Lies beneath the dermis.  mainly composed of loose connective tissue and adipose tissue. ***not strictly consider as part of the skin.  EPIDERMIS Composed of stratified squamous keratinized epithelium also contains melanocytes, Langerhan cells and Merkel’s cells. Consists of 5 layers of keratinocytes. Starting from dermis outwards:  Stratum Basale (germinativum)  Stratum Spinosum  Stratum Granulosum  Stratum Lucidum  Stratum Corneum Britney Spears Skin Glows Like Candy EPIDERMIS: Layers Innermost  Outermost  Stratum Basale (germinativum)  Stratum Spinosum  Stratum Granulosum  Stratum Lucidum*  Stratum Corneum  STRATUM BASALE o The deepest layer of epidermis. o Composed of single layer of cells resting on basement membrane. o Consists of columnar to cuboidal cells  Basal cell  Precursor cell  show intense mitotic activity giving raise to keratinocytes. o Forms the dermal-epidermal junction. o Involved in constant renewal of epidermal cells. o Human epidermis is renewed every 15-30 days. STRATUM BASALE: Cells  Melanocyte  Specialized cells in the stratum basale. Cellular  extend into the stratum extension of melanocyte spinosum Epidermis - long processes Pigment  Produces dark pigment  granules melanin - determine skin tone Golgi apparatus - stimulated by UV radiation Melanocyte nucleus Basement membrane Dermis  STRATUM SPINOSUM o Consists of polygonal keratinocytes cells. o Cytoplasmic process filled bundles of keratin filaments. o Filament form cellular extensions as spiny projections, which contain desmosomes at their tip. o The cytoplasmic filaments forms intercellular bridges which gives a spine studded appearance and these cells are called as prickle cells. o The keratin bundles resist the effects of abrasion. o Sole of foot has thicker stratum spinosum. Prickle cells/Spinous cell  Are keratin producing epidermal cells.  Contain numerous intracellular connection prickly appearances  Are held tightly to one another by desmosomes.  Made up the stratum spinosum.  Provide a continuous net-like layer of protection for underlying tissue. Malpighian layer of the skin  Site of mitotic activity.  Consists of stratum basale and stratum spinosum.  Layer of cells that produce pigment melanin.  STRATUM GRANULOSUM o Composed of 3-5 layers of flattened polygonal cells. o These cell contain basophilic granules called keratohyalin granules. o These granules contain phosphorylated histidine and cystine which are precursors of filaggrin  aggregates the keratin filaments present with in the cornified cells of stratum corneum.  Filaggrin  Is a filament aggregating protein.  Binds to keratin fibers in epithelial cells.  Plays an important role in the skin's barrier function.  It brings together structural proteins in the outermost skin cells to form tight bundles, flattening and strengthening the cells to create a strong barrier.  STRATUM LUCIDUM o More apparent and only found in thick skin. o Transculent, layer of extremely flattened, eosiniphilic epidermal cells. o Nuclei and organelles not evident. o Cytoplasm mainly contains densely packed keratin filaments.  STRATUM CORNEUM o Composed of layers of dead, non- nucleated, keratinized cells. o Made of flattened scale like elements (Squames) containing keratin filaments embedded in protein. Thin skin o Squames are held together by glue like material made up of lipids and carbohydrates. o It is thin in thin skin. Epidermal Cells MELANOCYTES  specialized cells found between or beneath cells of stratum basale.  Derived from neural crest cells.  Present with a rounded cell body, long branching extensions which pass into the stratum spinosum.  The colour of skin determined by  content of melanin and carotene pigment  Number of blood vessels in dermis  Types: *Eumelanin  A dark brown pigment produced by melanocyte. *Pheomelanin  pigment in red hair. *Neuromelanin  Found in the brain  LANGERHANS CELLS  Star shaped cells found in stratum spinosum.  2-8% of epidermal cells  Derivative of bone marrow.  They are responsible for binding, processing & presenting antigens to T lymphocytes. MERKEL CELLS  Specialised epidermal cells present in basal layer of epidermis.  Free nerve endings form a expanded terminal disk present at base of Merkels cells to form the Merkel’s corpuscle which is a sensitive mechanoreceptor. EPIDERMIS  DERMIS  Made up of connective tissue which binds the epidermis to hypodermis.  Thickness varies in different regions of body.  Very thick in skin of back  Surface of dermis very irregular due to the dermal papillae.  Dermal papillae are seen more in skin subjected to repeated pressure.  DERMIS  Consist of 2 layers: 1. Outer papillary layer 2. Inner reticular layer.  Numerous elastin & collagenous fibers interwoven between the 2 layers.  Dermis contain epidermal derivatives such as hair follicles,sweat and sebaceous glands.  Rich nerve supply. Effectors to skin are post ganglionic fibers of sympathetic ganglia. No parasympathetic innervation.  DERMIS: Cells  Fibroblasts – these cells synthesise the extracellular matrix, which is predominantly composed of collagen and elastin.  Mast cells – these are histamine granule-containing cells of the innate immune system. DERMIS: Layers  PAPILLARY LAYER projects into the stratum basale of the epidermis to form finger-like dermal papilla. *increase the strength of connection composed of loose connective tissue, type I and type II collagen fibers, elastic fibers, fibroblast and other connective tissue cells.  RETICULAR LAYER thicker, irregular dense connective tissue (type I collagen) more fibers and fewer cells. contains network of elastic fibers, arranged along regular lines of tension called as the Langer’s lines *along which surgical incisions are made.  CLINICAL APPLICATION Langer’s Cleavage Lines Also called as Langer lines of skin tension and cleavage lines. Are topological lines drawn on a map of the human body. Are parallel to the natural orientation of collagen fibers in the dermis, as well as the underlying muscle fibers. ideal for skin incisions in order for minimal tension across the wound, and result in a scar which fades amongst the natural creases on a patients face.  DERMIS: Blood supply Rich network of blood vessels and lymphatics. Arteries present as two plexuses:  Between papillary and reticular layer.  Between dermis and subcutaneous tissue.  PARTS OF SKIN: Epidermis Dermis Basement membrane TYPES OF SKIN: TYPES OF SKIN:  APPENDAGES OF THE SKIN DEF: Epidermal and dermal derived component of skin. Include:  Hair follicles and hair  Sweat glands  Sebaceous glands  Nails  Mammary glands  DEF: An elongated keratinized structure HAIR Hair formed by invagination of epidermal epithelium. Each hair arises from a hair follicle. Terminal dilatation  hair bulb -seen during growth period. At base of hair bulb  dermal papillae. Dermal papillae has capillary network, vital in sustaining hair follicle. * Loss of blood flow to dermal papillae results in death of hair follicle. The part of the hair embedded within the thickness of the skin  hair root. The shaft protrudes beyond skin.  HAIR FOLLICLE The hair follicle may be regarded as of epidermal invagination into the dermis around the hair root. It consists of 3 layers Inner root sheath- Cuticle Huxley’s Henle’s Outer root sheath- Continuation of stratum spinosum. Connective tissue sheath derived from dermis  Arrector pili muscle Bands of smooth muscles attached at one end to the dermis just below the dermal papillae and to the connective tissue sheath of the hair follicle at the other end. Contraction of the muscle  causes the hair follicle to become verticle, stand upright  Squeezes out the secretions of the sebaceous gland.  SWEAT GLANDS Sweat gland is a simple coiled tubular gland. The highly coiled body of the gland lies in the reticular layer of dermis. The gland drains through a duct which follows a spiral course through the epidermis and drains on the surface of the skin.  2 types of sweat gland:  Eccrine glands  Apocrine glands – the major sweat glands of the – larger sweat glands, located in human body. the axillary and genital regions. - release a clear, odourless - Release a thick, odorous fluid substance - their products can be broken - comprised mostly of sodium down by cutaneous microbes, chloride and water, which is producing body odour. involved in thermoregulation. SEBACEOUS GLANDS Sebaceous glands are seen close to the hair follicles. They are formed by a number of alveoli held together by connective tissue. Each alveolus consists of a The lipid is discharged by the solid mass of polyhedral disintegration of the inner cells which cells with hardly any lumen. are replaced by the proliferation of outer cells. The outer cells are small. The inner cells are large The secretion of sebaceous glands is and contain lipid. called sebum  NAIL  A complex structure located on the dorsal surface of the fingers and toes.  Function:  Protection – protects the digits  Components of nail: from trauma  Nail plate  Sensation  Nail fold – assists with tactile  Nail bed sensation  Germinal matrix  Hyponychium  Eponychium (cuticle)  Lunula Anatomy of Nail  SENSORY NERVE ENDINGS The nerves that innervate the epidermis. Most of the nerve fibers are found in the mid-dermis and the papillary dermis. Elicit all of the principal sensations: touch, pain, itch, warmth, and cold. They penetrate the dermis and ends in the stratum granulosum. Sensory receptors:  Mechanoreceptors – pressure/touch/pain  Thermoreceptors - temperature  Proprioceptors – stretching in muscle fibers, ligaments and tendons  Pain receptors  Chemoreceptors – specific chemicals  FUNCTIONS OF SKIN Impermeable to water, prevents water loss Receptor organ Protect against sun’s UV rays (Melanin) Thermoregulation Metabolism & Excretion Synthesis of vitamin D3 Certain regions of skin such as palm and sole show ridges and grooves in distinctive pattern.  The pattern may be in loops, arches or whorls.  These patterns are called as dermatoglyphics, unique in each individual and determined by multiple genes.  CLINICAL APPLICATION Psoriasis Increase in number of proliferative cells in stratum basale and spinosum and decrease in cycle time as a result greater epidermal thickness and more rapid renewal of epidermis. Albinism  Hereditary inability of melanocytes to synthesize melanin. Vitiligo  Degeneration and disappearance of entire melanocyte. Tumors of the skin in adults 1/3rd of all tumors. Basal cell carcinoma Squamous cell carcinoma Melanoma  Psoriasis Albinism Tinea Vitiligo versicolor  CLINICAL APPLICATION BURN An injury to the skin or other organic tissue primarily caused by heat or due to radiation, radioactivity, electricity, friction or contact with chemicals. References: Histology A Text and Atlas (Ross & Pawlina) Junqueira’s Basic Histology Wheater’s Functional Histology