Module 7 Structure and Function - SKIN and senses PDF

PN Structure and Function of Human Body Module 7 – Integumentary System Chapters 5 and 15  Overview This Module will cover the following topics/concepts: Layers of the skin (Integumentary System) Accessory structures of the Integumentary S...

PN Structure and Function of Human Body Module 7 – Integumentary System Chapters 5 and 15  Overview This Module will cover the following topics/concepts: Layers of the skin (Integumentary System) Accessory structures of the Integumentary System Functions of the Integumentary System. https://www.youtube.com/watch?a pp=desktop&v=63YdIH2S2ls Integumentary System (The Skin) SKIN Largest organ of the human body Approximately 16% of human body weight Complex structure composed of various tissues Comprises of Integumentary System Accessories Hair, nails, oil, sweat glands Consists of 3 layers held by connective tissue: Epidermis - made of closely packed epithelial cells (Keratinocytes) Site of pigment production (melanin) Site of keratin (regulated skin rigidity) Dermis - made of dense, irregular connective tissue that houses blood vessels, hair follicles, sweat glands, and other structures Hypodermis (or subcutaneous fat) - composed mainly of loose connective and fatty tissues.  Keratinocytes – the cells of the Epidermis Keratinocytes Primary type of cell found in the EPIDERMIS Constitute 90% of epidermal cells Basal cells are the precursor to keratinocytes. Function: Form a barrier against environmental damage by heat, UV radiation, water loss, pathogenic bacteria, fungi, parasites, and viruses. Role in wound healing – wounds to the skin will be repaired by the migration of keratinocytes to fill the gap created by the wound. Layers of the EPIDERMIS Four Layers*: 1. Stratum corneum (dead skin cells) 2. *Stratum lucidum (only present in the thicker skin of palms and soles) 3. Stratum granulosum (provide water proof barrier to prevent fluid loss) 4. Stratum spinosum (8-10 layers) 5. Stratum basale (base) 6. https://youtu.be/yKAzVC0WcmI?si=q7TJq Mo1KlQXP7XN  Strata of the Epidermis –Stratum Basale Stratum Basale Single row of basal cells undergoing rapid mitotic divisions. Often referred to as stem cells, replacing superficial keratinocytes lost at the surface. Cell Attachment: Hemidesmosomes connect cells to the basal lamina. Separates epidermis from the areolar tissue in the adjacent papillary layer of the dermis. Melanocytes: 10-25% of cells in this layer. Produce melanin, the skin pigment responsible for color. Specialized Cells - Merkel Cells: Found in hairless skin in small numbers. Sensitive to touch and release chemicals For clarification: upon compression, stimulating sensory 1. Areolar tissue is a versatile and essential type of connective tissue that provides support, flexibility, and a medium for nutrient and waste exchange throughout the body. Its loose nerve endings. and flexible structure makes it an integral part of many tissues and organs. 2. The areola is the circular pigmented area surrounding the nipple on the breast. 3. Two different things. Strata of the Epidermis – Stratum Spinosum Stratum Spinosum Composition: 8-10 layers of keratinocytes bound by desmosomes and pre-keratin microfilaments. Appearance: Cells resemble miniature pincushions, giving the layer its name. Dendritic Cells: 1. Abundant in this layer. 2. Specialized immune cells. 3. Defend against microorganisms and superficial skin cancers. Stratum spinosum plays a crucial role in skin defense, housing dendritic cells that actively contribute to immune responses. Stratum of the Epidermis – Stratum Granulosum, Stratum Lucidum and Stratum Corneum Epidermal Layers: Granulosum, Lucidum, Corneum 1. Stratum Granulosum: 3-5 layers, changing keratinocyte appearance. Named "grainy layer." Beyond, no nutrients. 2. Stratum Lucidum: In thick skin (palms, soles). Dead, dehydrating cells. 3. Stratum Corneum (Our Skin): Outermost, 15-30 keratinized layers. Keratinization for protection. Takes 7-10 days to reach, stays two weeks. Glycolipids provide waterproofing. Distinct layers showcase the skin's dynamic functions, from nutrient provision to waterproofing.  The DERMIS The DERMIS supports the epidermis, and the hypodermis connects the dermis to the rest of the body. The dermis lies between the epidermis and hypodermis. The dermis consists of two layers: Papillary layer Reticular layer  The Dermis – Papillary and Reticular Layer Dermal Layers: Papillary and Reticular 1.Papillary Layer: Highly vascularized areolar tissue. Houses capillaries, lymphatic vessels, and sensory neurons. Nourishes and supports the epidermis. Dermal papillae project between epidermal ridges. 2.Reticular Layer: Dense irregular connective tissue with collagen and elastic fibers. Collagen provides strength, elastic fibers offer flexibility. Restricts pathogen spread, stores lipids, attaches skin to deeper tissues. Contains sensory receptors and blood vessels for temperature regulation. Papillary and reticular layers play crucial roles in skin nourishment, support, and protection, showcasing a dynamic integration of structure and function.  Hypodermis Hypo = below or under The hypodermis separates the skin from deeper structures. It stabilizes the position of skin in relation to underlying tissues (such as skeletal muscles or other organs) while permitting independent movement. STUDENT INPUT: What Because it is often dominated by adipose tissue, the would a ‘hypodermic hypodermis also represents an important site for needle’ injection into? 1) insulation, 2) cushioning, and 3) the storage of energy reserves. Subcutaneous fat, muscle and veins are all HYPODERMIC Figure 5.8 Skin Pigmentation The relative coloration of the skin depends of the amount of melanin produced by melanocytes in the stratum basale and taken up by keratinocytes. Skin Colour Factors Influencing Skin Color 1.Genetic Programming and UV Response: Skin color genetically determined. Tanning response to ultraviolet radiation. 2.Epidermal Pigments: 1. Melanin Produced by melanocytes in the stratum basale. Colors range from brown to black. Manufactured from amino acid tyrosine. About 1000 melanocytes per sq. mm, variations in melanin production, not melanocyte numbers. 2. Carotene Orange-yellow pigment. Accumulates in epidermal cells and fatty tissues. Found in orange and yellow vegetables. 3.Albinism Inherited condition. Very light skin, hair, and eyes due to low melanin. Skin color is a result of genetic factors, melanin production, and responses to environmental influences like UV radiation, with variations in pigments contributing to the diversity of skin tones. Considerations for health care providers related to Melanin Variations Note: these videos are to demonstrate differences for your awareness. They are not from a referenced source and are not on your exam. This links below are available for you to read if you want to explore more on your own. https://www.tiktok.com/@joelbervell/video/7370148224142822699 https://www.tiktok.com/@joelbervell/video/6996083379586256133?q=joel%20bervell% 20oximeter&t=1716328576849 Videos by Joel Bervell (you tube) Related Articles from Pubmed Racial Disparities in Pulse Oximeter Device Inaccuracy and Estimated Clinical Impact on COVID-19 Treatment Course https://pubmed.ncbi.nlm.nih.gov/36173743/ Accuracy of Multiple Pulse Oximeters in Stable Critically Ill Patients; research done in 2023: Note that 96.2% of subjects were light skinned: https://pubmed.ncbi.nlm.nih.gov/36596654/ Figure 5.9 Moles Moles range from benign accumulations of melanocytes to melanomas. These structures populate the landscape of our skin. (credit: the National Cancer Institute) Figure 5.10 Vitiligo Individuals with vitiligo experience depigmentation that results in lighter colored patches of skin. The condition is especially noticeable on darker skin. (b) A photograph of the model Winnie Harlow, who has patches of unpigmented skin around her mouth and face. (credit: (a) Klaus D. Peter (b) Owl Bridge Media / Wikimedia.)  Hair A keratin filament from the epidermis, primarily consisting of dead cells. Grow from a structure called the hair follicle, penetrating the epidermis into the dermis Visible part is the hair shaft Anchored portion below is the hair root. Hair root ends at the hair bulb deep in the dermis (containing actively dividing cells) Hair bulb surrounds the hair papilla, which has blood vessels, and nerve endings from the dermis.  Nail bed is a specialized part of the epidermis at fingertips and toes Forms the foundation for the nail body, protecting high stress areas. Nails Nail body consists of dense, dead keratinocytes. Nail growth occurs at nail root, with a matrix of basal cells allowing continuous growth. Nail cuticle (eponychium) forms where the nail fold meets the proximal nail body. The pink appearance of nail bed due to its rich blood supply Sweat Glands or Sudoriferous glands Sweat Glands: Eccrine and Apocrine 1. Function: Produce sweat for body cooling. 2. Gland Types: Eccrine: Plays a vital role in thermoregulation. Releases mainly water, salt, antibodies, metabolic waste traces, and antimicrobial peptide dermicidin. Apocrine: Found in densely hairy areas (armpits, genital regions). Sweat contains organic compounds, making it thicker. Susceptible to bacterial decomposition, causing odor. Eccrine and apocrine sweat glands serve distinct purposes, contributing to body temperature regulation and maintaining hygiene in different regions. Sebaceous Glands Type of oil gland found all over body Help to lubricate and waterproof skin and hair. Most sebaceous glands associated with hair follicles Generate and excrete Sebum Sebum is a mixture of lipids. Fatty acids of the lipids have antibacterial properties, prevent water loss from skin STUDENT INPUT: What condition do you think is primarily a disorder of Sebum stimulated by hormones the sebaceous glands and hair follicles, involving excess sebum production, clogged pores, bacterial growth, and inflammation? ACNE  Absorption Elimination Excretion Function Fluid and Electrolyte Balance Hormone Production of Skin Immunity Insulation Protection Secretion Sensory Thermoregulation Figure 5.16 - Thermoregulation Thermoregulation: Because it has an enormous surface area During strenuous physical activities, such as skiing (a) or running (c), the dermal blood vessels dilate and sweat secretion increases (b). These mechanisms prevent the body from overheating. In contrast, the dermal blood vessels constrict to minimize heat loss in response to low temperatures (b). (credit a: “Trysil”/flickr; credit c: Ralph Daily) Figure 5.23 Calculating the Size of a Burn The size of a burn will guide decisions made about the need for specialized treatment. Specific parts of the body are associated with a percentage of body area. Introduction to the Senses Chapter 15 Image: https://incident-prevention.com/blog/are-you-using-your-five-senses-to-stay-safe/  Gustation - Taste Taste perception – part of the sensory system Detects taste, initially recognizing four basic tastes: sweet, salty, sour and bitter. Tongue is the primary organ associated with gustation (taste perception) Epithelium: Lined with stratified squamous epithelium. Taste Buds: Papillae house taste structures. Gustatory Cells: Respond to food chemicals, release neurotransmitters. Neural Activation: Activates sensory neurons in facial, glossopharyngeal, and vagus nerves. Tongue anatomy and gustatory cells link taste detection to neural signals for a comprehensive gustatory experience. Olfaction – Smell Olfaction, the sense of smell, responds to chemical stimuli Olfactory receptor neurons are in the olfactory epithelium in the nasal cavity. Odorant molecules dissolve in mucus and bind to proteins. These molecules interact with receptor proteins on olfactory dendrites, generating membrane potential changes. Olfactory neurons send signals to the brain when we smell things. These signals go to the olfactory bulb, like a central processing hub. From there it goes to different parts of the brain. The temporal lobe identifies smells, and the limbic system connects smells to memories and emotions. https://www.youtube.com/watch?v=wQJbsOWc344 Audition - Hearing Audition involves converting sound waves into neural signals through ear structures. The auricle (pinna) on the head directs sound waves into auditory canal. The canal leads to the tympanic membrane (eardrum), which vibrates when struck by sound waves. Outer ear structures. These external parts make up the external ear. https://www.youtube.com/watch?v=C6Z QUmBg1eU  Structures of the Ear The middle ear contains three small bones: malleus, incus and stapes, which transmit vibrations. The eustachian tube connects the middle ear to the pharynx to equalize air pressure. It does this by opening during activities such as swallowing, yawning or the Valsalva maneuver Eustachian tube Part bony, part cartilage THE PATHWAY OF SOUND THROUGH THE EAR External auditory canal tympanic membrane (Eardrum)  ossicle oval window  hair cells in organ of Corti cochlear nerve (branch of cranial nerve VIII Cochlea Inner Ear: Hearing and Balance 1. Structures: Inner ear in the temporal bone includes the cochlea (hearing) and vestibule (balance). 2. Sound Transduction: Sensory neurons in the cochlea transduce sound into neural signals. 3. Cochlea Connection: Cochlea connected to stapes via the oval window. 4. Fluid Motion: Cross Section of the Cochlea Sound waves cause fluid motion in the scala tympani of the cochlea. 5. Round Window Response: Round window membrane responds to fluid movement, matching sound wave frequencies. 6. Organ of Corti: Contains hair cells (stereocilia) responding to membrane movements caused by waves. The inner ear, with its cochlea and vestibule, plays a dual role in hearing and balance, showcasing a remarkable interplay of structures for sensory functions.  The Vestibular System - Equilibrium Inner Ear and Equilibrium 1. Equilibrium Encoding: Inner ear encodes information about equilibrium, the sense of balance. 2. Mechanoreceptors: Hair cells with stereocilia act as mechanoreceptors. Sense head position, movement, and body motion. 3. Utricle and Saccule: Utricle and saccule sense head position. 4. Nervous System Transmission: Information travels through nerves to the brain stem and cerebellum. 5. Fluid Movement: When you turn your head, fluid moves in the canals. Bending hair cells convey head movement to the brain. The inner ear, through mechanoreceptors and fluid dynamics, plays a crucial role in encoding information about head position and movement for maintaining balance  Where does conversions of sound vibrations to nerve impulses take place (receptor of hearing)? Cerumen collects in what part of the ear? Knowledge check Tempanic Membrane is external or internal ear? What are the structures found in the middle ear? VISION Anatomy of the Eyes 1. Sense of Sight: Vision is the sense of sight, relying on capturing and processing light through the eyes. 2. Eye Location: Eyes are situated within the bony orbits in the skull. 3. Protective Orbits: Orbits protect and hold the eyes in place. 4. Eyelids and Eyelashes: Eyelids, with eyelashes, shield the eyes from harmful particles. 5. Palpebral Conjunctiva: Inner eyelid surface connecting eyelids to the eyeball. 6. Tear Production: Tears produced by the lacrimal gland near the nose. 7. Lacrimal Duct: Tears flow through the lacrimal duct to the inner corner of the eye. 8. Conjunctiva Cleansing: Tears wash over the conjunctiva, helping remove foreign particles. The eyes, protected by orbits, eyelids, and tears, play a crucial role in the sense of sight, highlighting the intricate anatomy for visual function Eye Anatomy Video https://www.youtube.com/watc h?v=8gRpjwmbdJQ  Extraocular Muscles Eye movement is controlled by six extraocular muscles connected to the eye. These muscles help with eye movement Superior rectus moves the eye up Inferior rectus moves the eye down. Medial rectus moves eye inward Lateral rectus moves eye outward Levator palpebrae superioris raises upper eyelid. These muscles are connected to different cranial nerves that control their movement.  PATHWAY OF LIGHT THROUGH THE EYE cornea aqueous humor  pupil  lens vitreous humour -rods and cones in the retina  optic nerve (cranial nerve II) Intraoccular pressure: Pressure of the aqueuos Humor inside the eye  Which eye disease can lead to permanent loss of vision: Cataracts or glaucoma? Knowledge 2. Pathway of light in the eye? Check??? 3. What do we call the pressure of the aqueous humor? The end