NURS 207 (N01) Skin Type, Function, Wound Healing, and Epithelial Transport (October 7, 2024) PDF

NURS 207 (N01) Skin (cutaneous membrane) Skin type, function, wound healing and epithelial transport Reading materials (textbook): Tortora, 16th ed., Ch. 5 October 7, 2024 Dr. P. Lee  Objectives 1) C...

NURS 207 (N01) Skin (cutaneous membrane) Skin type, function, wound healing and epithelial transport Reading materials (textbook): Tortora, 16th ed., Ch. 5 October 7, 2024 Dr. P. Lee  Objectives 1) Compare structural and functional differences in thin and thick skin 2) List the physiological functions of the skin 3) Describe how the integumentary system contributes to homeostasis 4) Explain how epidermal wounds and deep wounds heal 5) Describe the processes involving epithelial transport mechanisms i.e. transportation between compartments within the body across a layer of epithelial cells  Review: 5 layers in a typical epidermis 1) Stratum corneum → Layers of flattened dead keratinocytes (absence in nucleus and internal organelles) 2) Stratum lucidum → Present mostly in the thick skin of areas such as the fingertips, palms, and soles 3) Stratum granulosum → With flattened keratinocytes that are undergoing apoptosis 4) Stratum spinosum → Cells are appeared to be covered with thorn-like spines 5) Stratum basale → Deepest layer of the epidermis  Structural and functional differences in thin and thick skin ❖ Two major types of skin (thick and thin): Classification base upon their structural and functional properties Thin skin Thick skin All parts of body Areas such as palms, Location except areas thick palmar surface of skin are found digits, and soles Thickness 0.10 – 0.15 mm 0.6 – 4.5 mm  Thin skin Thick skin Hairy (with arrector Hairless (without Hair pili muscles) arrector pili muscles) Stratum lucidum (2nd Stratum lucidum Epidermal layer) essentially present; thicker strata lacking, with thinner strata corneum and strata corneum and spinosum spinosum Sebaceous Present Absent glands Sudoriferous Fewer More (sweat) glands Sensory Fewer More receptors  Functions of the skin (to maintain homeostasis) Thermoregulation → Through the dilatation or constriction of the blood vessels Body protection → Keratin protects underlying tissues → Reduce evaporation through the secretion by lamellar granules (also contain bactericidal chemicals) → Melanin protect UV damage → Intraepidermal macrophages as the immune system  Functions of the skin Cutaneous sensations → Provides sensory information such as pleasure, pain, texture, temperature etc. Vitamin D production → Precursor required for the synthesis of biologically inactive form of vitamin D is found in skin → Precursor is activated when exposed to UV-B light (converted to biologically active form in kidneys) Excretion → Water, salts, ammonia & urea Absorption → Topical steroids (applied to the skin) Epidermal wounds and deep wounds healing  Skin wound healing ❖ 2 types: epidermal & deep wounds healing → Depending on the depth of the injury 1) Epidermal wound healing: → Usually involves superficial epidermal layer injury at the edge of the wound → Might involves the dermis at the central portion of the epidermal wound  Skin wound healing 1) Epidermal wound healing: Superficial epidermal injury Basal cells surrounding the wound break contact with the basal membrane Basal cells around the wound enlarge and migrate toward each other until they meet Growth, proliferation and Migration stop differentiation of the basal when they meet cells is stimulated by the (contact inhibition) epidermal growth factor  Skin wound healing 2) Deep wound healing: → Trauma extended to dermis and subcutaneous layer → Healed tissue might lose some of the normal function resulting from the formation of scar tissue  Skin wound healing 2) Deep wound healing: Four phases: i. Inflammatory phase ii. Migratory phase iii. Proliferative phase iv. Maturation phase  Skin wound healing Blood clot 2) Deep wound healing: Phase 1: Inflammatory phase → With blood clot adhere loosely to the wound edges (vascular damage) → Require appropriate response for the elimination and removal of microbes, foreign substance, and dead tissues (initiate the inflammatory response) ▪ Inflammatory phase is essential for the preparation of tissue repair  Skin wound healing 2) Deep wound healing: Phase 1: Inflammatory phase → Inflammation is a non- specific defensive response to tissue damage → has 3 stages: ▪ Vasodilation and increase vascular permeability ▪ Phagocyte emigration → leaving the blood vessel ▪ Tissue repair  Skin wound healing 2) Deep wound healing: Phase 1: Inflammatory phase ❖ Three types of cells are involved: Two types of phagocytes ▪ Neutrophils & monocytes (macrophages) → Phagocytize microbes, foreign substance, and dead tissues Fibroblasts → Transform into extracellular matrix and collagen (critical role in wound healing)  Skin wound healing 2) Deep wound healing: Phase 2: Migratory phase ✓ Clot becomes a scab → Incrustation that covers a wound during healing ✓ 2 to 3 days after the injury, fibroblasts begin to migrate to the site of injury → Fibroblasts start producing structural molecules (scar tissue) containing collagen fibers and glycoproteins → Angiogenesis (regrow of blood vessels) begins  Skin wound healing 2) Deep wound healing: Phase 3: Proliferative phase ✓ With extensive growth of the epithelial cells beneath the scab ✓ angiogenesis and fibroblast proliferation occur at the same time → Fibroblast proliferation peaks at one to two weeks and end at 2 to 4 weeks post-wounding → Fibroblasts is the key cell to form the collagen matrix in the wound site, increase the strength of the wound and hold the wound close  Skin wound healing 2) Deep wound healing: Phase 4: Maturation phase ✓ Degradation of of the scab ✓ Epidermis thickness restored to normal thickness ✓ Collagen fibers become more organized ✓ Fibroblast population decreases and blood circulation restore back to normal ✓ Onset of the maturation phase can varies from days to year, or longer, depending whether the wound is closed or left open and the wound size Epithelial transport  Epithelial transport → Epithelium are layer of tissues line the cavity, organs, or surface structures throughout the body → Epithelial transport involves moving substances across 2 membranes → Surface of the lining that faces the lumen (cavity) of an organ is called the apical membrane → Surface of the lining that faces the extracellular fluid is called the basolateral membrane  Stomach Apical surface Parietal cells secrete HCl into the lumen of the stomach. Tight junctions prevent Capillary transport through the paracellular pathway. Lumen of Interstitial stomach fluid H2O H+ H+ + OH− ATP K+ CA K+ HCO3− HCO3− CO2 Cl− Cl− Cl− Parietal Cl− cells Parietal cell Basolateral surface  Epithelial transport → Concentration gradient for ions or molecules are usually difference between intra and extracellular compartments → Requires different transporters to transport the substances from the lumen into the cell and from the cell (intracellular) to the extracellular compartments  Epithelial transport of glucose in small intestine Lumen of kidney [Glucose]low Glu Na+ [Na+]high Na+-glucose symporter or intestine (SGLT) Luminal to intracellular through the apical membrane Apical membrane Glucose transporter [Glucose]high Glu Na+ [Na+]low (GLUT) Epithelial cell Intracellular to extracellular through the basolateral membrane Basolateral membrane Glu Na+ K+ Na+-K+-ATPase pumps ATP To maintain concentration Extracellular gradient between intracellular fluid [Glucose]low Glu [Na+]high Na+ K+ and extracellular  Epithelial transport – directional Lumen of intestine or kidney Apical membrane with microvilli faces the lumen. Secretion Transporting epithelial cell Tight junction Absorption limits movement (transcellular) of substances between the cells. Transport proteins Absorption (paracellular) Basolateral membrane faces the ECF. Extracellular fluid → Different transport proteins allow for directional transport across the epithelium → Transport from lumen to ECF is called absorption → Transport from ECF to lumen is called secretion  Epithelial transport Lumen of intestine or kidney Apical membrane with microvilli faces the lumen. Secretion Transporting epithelial cell Tight junction Absorption limits movement (transcellular) of substances between the cells. Transport proteins Absorption (paracellular) Basolateral membrane faces the ECF. Extracellular fluid → There are 2 types of epithelial transport: i) Paracellular transport - Through junctions between adjacent cells  Epithelial transport Lumen of intestine or kidney Apical membrane with microvilli faces the lumen. Secretion Transporting epithelial cell Tight junction Absorption limits movement (transcellular) of substances between the cells. Transport proteins Absorption (paracellular) Basolateral membrane faces the ECF. Extracellular fluid ii) Transcellular transport → By means of transcytosis → Through both the apical and basolateral membrane with the help of carrier proteins (channels), or  Epithelial transport ii) Transcellular transport Transcytosis → Combination of endocytosis, vesicular transport across the cytoplasmic space, and exocytosis → Allow the transport of macromolecules through apical-basolateral membranes, or the reverse direction, and remain intact  Red blood Plasma proteins cell Caveolae Endocytosis Capillary endothelium Vesicular transport Interstitial fluid Exocytosis Plasma proteins Vesicles cross Vesicle contents are concentrated the cell with are released into in caveolae, which help from the interstitial fluid then undergo cytoskeleton. by exocytosis. endocytosis and form vesicles. Transcytosis across the capillary endothelium  Sample questions 1) Choose the following statements that describe keratin. a) Keratin participates in immune responses b) Keratin is used for pigmenting skin c) Keratin is the fibrous protein produced by keratinocytes d) Keratin protects the skin from UV light damage 2) Which of the followings is secreted by specialized cells in the skin that is capable of absorbing ultraviolet light? a) Melanin b) Carotene c) Melatonin d) Hemoglobin  Sample questions 3) Which of the following structures found in the skin has the function to prevent water loss on the surface of the skin? a) Arrector pili muscle b) Lamellar granules c) Melanin granules d) Intraepidermal macrophages 4) Which of the following statements is CORRECT? a) All the cells located within the epidermal layer of the skin are dead cells b) Hypodermis is part of the cutaneous membrane c) Exposure to UV enhance the production of vitamin D d) Keratin is packaged within the lamellar granules  Sample questions 5) Which of the following statements is CORRECT? a) All types of skin contain arrector pili muscles b) Sebaceous glands can be found in both the thick and thin skin c) There are more sudoriferous (sweat) glands in thin than thick skin d) There are more sensory receptors in thick than thin skin 6) Which of the followings is NOT the functions of skin? a) Thermoregulation b) Production of keratin to protect UV damage c) Production of vitamin D when expose to UV light d) Provides sensory information  Sample questions 7) Epidermal wound and wound healing usually involve all of the followings, EXCEPT: a) Basal cells surrounding the wound will break contact with the basal membrane b) Dermal layer can be at the central portion of the wound c) Migration of the basal cells around the wound will stop when they come in contact with each other d) Basal cells around the wound will decrease in size and migrate toward each other until they meet 8) Which of the followings is the best answer related to deep wound healing? a) Phagocytosis is essential for the initiation of the inflammatory response b) Vasodilation occurs during the inflammatory phase c) Angiogenesis occurs in migratory and proliferative phase d) All of the above are correct  Answer to sample questions 1) c 2) a 3) b 4) c 5) d 6) b 7) d 8) d