A&P I Lecture 6: Embryonic Development and Integumentary System

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What is development in the context of embryology?: The gradual modification of anatomy and physiology from fertilization to maturity.
What are the two main phases of prenatal development?: Embryological and fetal stages.
What occurs during the first trimester of prenatal development?: Embryological and early fetal development.
What is the primary focus of the second trimester?: Development of organs and systems, and changes in body proportions.
What happens during the third trimester of prenatal development?: Fetal weight gain and functional maturation of organ systems.
What is fertilization?: The fusion of two haploid gametes to form a zygote.
Where does fertilization typically occur?: In the uterine tube, specifically at the ampulla or isthmus.
How many sperm typically reach the isthmus during fertilization?: About 100 sperm out of approximately 200 million.
What is the first step of fertilization?: Oocyte at ovulation is suspended in metaphase II.
What occurs during sperm contact and oocyte activation?: Acrosomal enzymes breach the corona radiata.
What is amphimixis in the fertilization process?: The fusion of female and male pronuclei to form a zygote.
What is cleavage in embryonic development?: Rapid cell division without growth, leading to the formation of blastomeres.
What is a morula?: A solid ball of cells formed around day 3 after fertilization.
What is a blastocyst?: A hollow ball of cells with a blastocoele formed around day 5.
When does implantation of the blastocyst begin?: Around day 7, when the blastocyst adheres to the endometrium.
What is gastrulation?: The process where cells move inward to form the three primary germ layers.
What are the three primary germ layers formed during gastrulation?: Ectoderm, mesoderm, and endoderm.
What does the ectoderm develop into?: The nervous system and skin.
What does the mesoderm develop into?: Muscle, bone, and blood.
What does the endoderm develop into?: The gut, liver, and lungs.
What key development occurs during week 1 of embryonic development?: Cleavage and implantation.
What significant event occurs during week 4 of embryonic development?: Closure of the neural tube and formation of somites.
When does the heart begin to beat during embryonic development?: Around day 22.
When do the eyes and ears begin to form during embryonic development?: By week 6.
What is the integumentary system?: The largest, most accessible organ system comprising the cutaneous membrane and accessory structures.
What percentage of total body weight does the integumentary system make up?: ~16%
What are the two main components of the cutaneous membrane?: Epidermis and dermis.
What is the hypodermis?: The layer below the dermis that separates the integument from underlying fascia and contains adipose tissue.
What are the functions of the hypodermis?: Stabilizes skin and allows independent movement over deeper structures.
What are the accessory structures of the skin?: Hair, sebaceous glands, sweat glands, nails, and sensory receptors.
What type of tissue primarily makes up the epidermis?: Stratified squamous epithelium.
How many layers are in thick skin?: Five layers.
What is the stratum corneum?: The outermost protective layer of the epidermis composed of dead, keratinized cells.
What is the role of melanocytes?: To produce melanin, which affects skin pigmentation.
What pigment gives skin its orange-yellow color?: Carotene.
What is cyanosis?: A blue tint visible in thin skin areas when oxygen levels are low.
What are the two layers of the dermis?: Papillary layer and reticular layer.
What is the primary function of sebaceous glands?: To secrete sebum, which lubricates hair and skin.
What are the two types of hair?: Terminal hairs (thick, pigmented) and vellus hairs (thin, short, light).
What is the hair growth cycle's active phase called?: Anagen phase.
What is the function of sweat glands?: To cool the skin, excrete wastes, and provide antibacterial properties.
What is the role of tactile corpuscles?: To detect light touch in the skin.
What is the clinical significance of nails?: Nail abnormalities can indicate systemic conditions.
What is the function of arrector pili muscles?: To raise hair, causing goosebumps.
What happens to hair color as a person ages?: Pigment production decreases, leading to gray or white hair.
What is the role of free nerve endings in the skin?: To detect pain and temperature.
What are lines of cleavage?: Orientation of collagen and elastin fibers in the dermis important for surgical incisions.
What are the two types of sweat glands?: Apocrine and merocrine (eccrine) sweat glands.
What is the function of the lunula in nails?: It is the pale crescent at the nail base that indicates nail growth.
What is the significance of the stratum granulosum?: It contains keratinocytes that stop dividing and start producing keratin.
What is the primary component of the dermis?: Collagen and elastin fibers.
What is the function of myoepithelial cells in sweat glands?: To squeeze the gland to discharge sweat.
What are tactile discs?: Touch receptors in the epidermis monitored by Merkel cells.
What is the most common type of skin cancer?: Basal cell carcinoma
Where does basal cell carcinoma originate?: In the stratum basale due to UV exposure
Does basal cell carcinoma metastasize?: Rarely metastasizes; has a high survival rate
What type of cells are involved in malignant melanoma?: Cancerous melanocytes
How does malignant melanoma metastasize?: Through the lymphatic system
What is the 5-year survival rate for malignant melanoma if detected early?: 99% if detected early; 14% if after metastasis
What are some age-related changes in the skin?: Fewer melanocytes, thinning epidermis, diminished immune response, thinning dermis, decreased perspiration
What hormonal effect do glucocorticoids have on the skin?: Weaken intercellular connections and reduce epidermal barrier function
What is the role of thyroid hormones in skin function?: Maintain blood flow to the papillary plexus
How do sex hormones affect the skin?: Increase epidermal thickness, accelerate wound healing, and boost dendritic cell numbers
What does Epidermal Growth Factor (EGF) promote?: Division in stratum basale/spinosum, speeds up keratin production and repair, stimulates glands
What is the source of Vitamin D3?: Sunlight (UV converts steroids in skin to cholecalciferol) and diet (fish, oils, fortified products)
What condition is caused by a lack of sunlight and insufficient dietary cholecalciferol?: Rickets
What occurs during the initial phase of skin repair after injury?: Bleeding and inflammation from mast cells, followed by scab formation and macrophage activity
What happens after one week in the skin repair process?: The clot dissolves partially, fibroblasts deposit collagen and matrix, and capillaries decline
What occurs after several weeks in the skin repair process?: The scab falls off, the epidermis is repaired, and scar tissue elevates the epithelium
What is granulation tissue?: A combination of blood clot, fibroblasts, and an extensive capillary network formed during skin repair
What happens to severely damaged hair follicles and glands during skin repair?: They are seldom repaired and replaced by fibrous tissue
How does the dermis change after skin repair?: It contains an abnormally large number of collagen fibers and relatively few blood vessels