Chapter 4 Skin and Body Membranes Body Membranes Functions of body membranes Cover body surfaces Line body cavities Form protective sheets around organs Classified according to tissue types Body Membranes Two major categories Epithelial membranes Cutaneous membranes Mucous membranes Serous membranes Connective tissue membranes Synovial membranes Epithelial Membranes Epithelial membranes are simple organs Also called covering and lining membranes These membranes contain both: Epithelial tissue layer Connective tissue layer Epithelial Membranes Cutaneous membrane = skin Dry membrane Outermost protective boundary Consists of two layers Epidermis is composed of keratinized stratified squamous epithelium Dermis is mostly dense (fibrous) connective tissue Epithelial Membranes • Mucous membranes (mucosae) • I Moist membranes Some mucosae secrete protective, lubricating mucus Line all body cavities that open to the exterior body surface • Adapted for absorption or secretion • ' Consists of two layers • Epithelium type depends on site • Loose connective tissue (lamina propria) Epithelial Membranes Serous membranes (serosae) Line compartments in the ventral body cavity that are ciosed to the exterior of the body Occur in pairs, separated by serous fluid, with a visceral and parietal layer Consists of two layers Simple squamous epithelium Areolar connective tissue Epithelial Membranes Specific serous membranes Peritoneum Cover organs in the abdominal cavity Pleurae Surround the lungs Pericardia Surround the heart Connective Tissue Membranes Synovial membranes Loose areolar connective tissue only (no epithelial tissue) Line fibrous capsules surrounding joints Line bursae Line tendon sheaths Secrete a lubricating fluid to cushion organs moving against each other during muscle activity Integumentary System Integumentary system consists of the: Skin (cutaneous membrane) Skin appendages Sweat glands Oil glands Hair Nails Functions of the Integumentary System Insulates and cushion deeper body organs Protects the entire body from: Mechanical damage (bumps and cuts) Chemical damage (acids and bases) Thermal damage (heat or cold) Ultraviolet (UV) radiation (sunlight) Microbes (bacteria) • Water loss Functions of the Integumentary System Regulates heat loss as controlled by the nervous system Acts as a mini-excretory system; sweat aids in the loss of Urea Salts Water Synthesizes vitamin D Secretions create a protective acid mantle Structure of the Skin Two kinds of tissue compose the skin Epidermis Dermis Subcutaneous tissue (hypodermis) Anchors the skin to underlying organs Not technically part of the integumentary system Composed mostly of adipose tissue Serves as a shock absorber and insulates deeper tissues Structure of the Skin Epidermisouter layer Composed of stratified squamous epithelium Most cells are keratinocytes which produce a fibrous protein called keratin Keratinization makes the epidermis tough Desmosomes connect keratinocytes together Avascular Composed of five layers (strata) Structure of the Skin Summary of strata (layers) of the epidermis from deepest to most superficial Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum (thick, hairless skin only) Stratum corneum Structure of the Skin Stratum basale (stratum germinativum) Deepest layer of epidermis Lies next to dermis Wavy borderline with the dermis anchors the two together Cells undergoing mitosis Daughter cells are pushed upward to become the more superficial layers Stratum spinosum Cells become increasingly flatter and more keratinized Structure of the Skin Stratum granulosum Stratum lucidum Formed from dead cells of the deeper strata Occurs only in thick, hairless skin of the palms of hands and soles of feet Stratum corneum Outermost layer of epidermis Shingle-like dead cells are filled with keratin (protective protein prevents wat loss from skin Structure of the Skin Melanin Melanin is a pigment produced by melanocytes Melanocytes are mostly in the stratum basale of the epidermis Color is yellow to brown to black Structure of the Skin Epidermal dendritic cells Alert and activate immune cells to a threat (bacterial or viral invasion) Merkel cells Associated with sensory nerve endings Serve as touch receptors called Merkel discs Structure of the Skin Dermis Connective tissue Underlies the epidermis Two regions Papillary Reticular Structure of the Skin Two regions of the dermis Papillary layer (upper dermal region) contain projections called dermal papillae Areolar connective tissue Indent the epidermis above Many projections contain capillary loops, and others house pain and touch receptors On palm and sole surfaces, papillae increase friction and gripping ability Fingerprints are identifying films of sweat Structure of the Skin Two regions of the dermis Reticular layer (deepest skin layer) Dense irregular connective tissue Blood vessels Sweat and oil glands Deep pressure receptors (lamellar corpuscles) Structure of the Skin Other dermal features Cutaneous sensory receptors Phagocytes Collagen and elastic fibers Blood vessels I Nerve supply Skin Color • Three pigments contribute to skin color 1. Melanin • Yellow, reddish brown, or black pigments 2. Carotene • Orange-yellow pigment (also found in some vegetables) 3. Hemoglobin Red coloring from blood cells in dermal capillaries Oxygen content determines the extent of red coloring Skin Color Redness (erythema) due to embarrassment, inflammation, hypertension, fever, or allergy Pallor (blanching) due to emotional stress (such as fear), anemia, low blood pressure, impaired blood flow to an area Jaundice (yellow cast)-indicates a liver disorder • Bruises (black and blue marks)-hematomas Appendages of the Skin Cutaneous glands are all exocrine glands Sebaceous glands Sweat glands Hair and hair follicles Nails Appendages of the Skin Sebaceous (oil) glands Located all over the skin except for palms and soles Produce sebum (oil) Makes skin soft and moist Prevents hair from becoming brittle Kills bacteria Most have ducts that empty into hair follicles; others open directly onto skin surface Glands are activated at puberty with increased androgens Appendages of the Skin Sweat (sudoriferous) glands Produce sweat Widely distributed in skin Two types of sudoriferous glands Eccrine glands Apocrine glands Appendages of the Skin Eccrine glands More numerous, located all over the body Open via duct to sweat pores on the skin's surface Produce acidic sweat Water, salts, vitamin C, traces of metabolic waste Function in body temperature regulation Appendages of the Skin Apocrine glands Ducts empty into hair follicles in the armpit and genitals Begin to function at puberty Release sweat that also contains fatty acids and proteins (milky or yellowish color) • Play a minimal role in body temperature regulation Appendages of the Skin Hair Located body-wide except for palms, soles, nipples, lips Produced by hair follicle Root is enclosed in the follicle Shaft projects from the surface of the scalp or skin Consists of hard keratinized epithelial cells Melanocytes provide pigment for hair color Hair grows in the matrix of the hair bulb in stratum basale Appendages of the Skin Hair anatomy Central medulla Cortex surrounds medulla Cuticle on outside of cortex Most heavily keratinized region of the hair Melanin provides color Appendages of the Skin Associated hair structures Hair follicle Composed of an inner epithelial root sheath andan outer fibrous sheath Dermal region provides a blood supply to the hair bulb (deepest part of the follicle) Arrector pili muscle connects to the hair follicle to pull hairs upright when we are cold or frightened Appendages of the Skin Nails Heavily keratinized, scalelike modifications of the epidermis Stratum basale extends beneath the nail bed, which is responsible for growth Lack of pigment makes nails colorless Appendages of the Skin Parts of a nail Free edge Body is the visible attached portion Nail folds are skin folds that overlap the edges of the nail; the cuticle is the proximal edge Root of nail is embedded in skin Growth of the nail occurs from nail matrix of nail bed Homeostatic Imbalances of Skin Infections and allergies Athlete's foot Caused by fungal infection (Tinea pedis) Itchy, red peeling skin between the toes Boils (furuncles) and carbuncles Caused by inflammation of hair follicles Carbuncles are clusters of boils caused by bacteria Cold sores (fever blisters) Caused by human herpesvirus 1 Blisters itch and sting Homeostatic Imbalances of Skin Infections and allergies Contact dermatitis Caused by exposure to chemicals that provoke allergic responses Itching, redness, and swelling of the skin Impetigo Caused by bacterial infection Pink, fluid-filled raised lesions around mouth/nose Psoriasis Triggered by trauma, infection, hormonal changes, or stress Red, epidermal lesions covered with dry, silvery scales that itch, burn, Crack, or sometimes bleed Homeostatic Imbalances of Skin • Burns Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals Associated dangers Protein denaturation and cell death Dehydration and electrolyte imbalance Circulatory shock Result in loss of body fluids and infection from the invasion of bacteria Homeostatic Imbalances of Skin Extent of a burn is estimated using the rule of nines Body is divided into 11 areas for quick estimation Each area represents about 9 percent of total body surface area The area surrounding the genitals (the perineum) represents 1 percent of body surface area Homeostatic Imbalances of Skin . First-degree burn (superficial burn) Only epidermis is damaged Skin is red and swollen Second-degree burn (superficial partial-thickness burn) Epidermis and superficial part of dermis are damaged Skin is red, painful, and blistered Regrowth of the epithelium can occur Homeostatic Imbalances of Skin Third-degree burn (full-thickness burn) Destroys epidermis and dermis; burned area is painless Requires skin grafts, as regeneration is not possible Burned area is blanched (gray-white) or black Fourth-degree burn (full-thickness burn) Extends into deeper tissues (bone, muscle, tendons) Appears dry and leathery Requires surgery and grafting May require amputation Homeostatic Imbalances of Skin Criteria for deeming burns critical (if any one is met): Over 30 percent of body has second-degree burns Over 10 percent of the body has third-or fourth-degree burns Third-or fourth-degree burns of the face, hands, feet, or genitals Burns affect the airways Circumferential (around the body or limb) burns have occurred Homeostatic Imbalances of Skin Skin cancer Most common form of cancer in humans Most important risk factor is overexposure to ultraviolet (V) radiation in sunlight and tanning beds Cancer can be classified two ways Benign means the neoplasm (tumor) has not spread Malignant means the neoplasm has invaded other body areas Concept Link Recall that mitosis gone wild is the basis for cancer (Chapter 3, pp. 82-83). These cells lack normal control of cell division and divide quickly, resulting in errors during DNA replication, mitosis, or both. Cells experiencing rapid, uncontrolled growth become cancerous and can metastasize (spread) to other parts of the body. Homeostatic Imbalances of Skin . First-degree burn (superficial burn) Only epidermis is damaged Skin is red and swollen Second-degree burn (superficial partial-thickness burn) Epidermis and superficial part of dermis are damaged Skin is red, painful, and blistered Regrowth of the epithelium can occur Homeostatic Imbalances of Skin Third-degree burn (full-thickness burn) Destroys epidermis and dermis; burned area is painless Requires skin grafts, as regeneration is not possible Burned area is blanched (gray-white) or black Fourth-degree burn (full-thickness burn) Extends into deeper tissues (bone, muscle, tendons) Appears dry and leathery Requires surgery and grafting May require amputation Homeostatic Imbalances of Skin Criteria for deeming burns critical (if any one is met): Over 30 percent of body has second-degree burns Over 10 percent of the body has third-or fourth-degree burns Third-or fourth-degree burns of the face, hands, feet, or genitals Burns affect the airways Circumferential (around the body or limb) burns have occurred Homeostatic Imbalances of Skin Skin cancer Most common form of cancer in humans Most important risk factor is overexposure to ultraviolet (V) radiation in sunlight and tanning beds Cancer can be classified two ways Benign means the neoplasm (tumor) has not spread Malignant means the neoplasm has invaded other body areas Concept Link Recall that mitosis gone wild is the basis for cancer (Chapter 3, pp. 82-83). These cells lack normal control of cell division and divide quickly, resulting in errors during DNA • One or more of the ABCD characteristics is evolving Developmental Aspects of Skin and Body Membranes Lanugo, a downy hair, covers the body by the fifth or sixth month of fetal development but disappears by birth Vernix caseosa, an oily covering, is apparent at birth Milia, small white spots, are common at birth and disappear by the third week Acne may appear during adolescence Pimples, scales, and dermatitis are more common with aging skin Developmental Aspects of Skin and Body Membranes In youth, skin is thick, resilient, and well hydrated With aging, skin loses elasticity and thins Skin cancer is a major threat to skin exposed to excessive sunlight Balding (alopecia) and/or graying occurs with aging; both are genetically determined other factors that may contribute include drugs and emotional stress

Lecture InfoSpeaker / Instructor: InstructorCourse / Subject: Histology / Epithelial tissueMain ThemeEpithelia are cellular sheets that protect, secrete, and absorb; structure (cellularity, polarity, surface specializations) determines function and clinical behavior.Key TakeawaysBarrier principle: "Nothing gets into the body unless it crosses an epithelium." Epithelium is the primary barrier to entry.Polarity: Apical vs basal surfaces differ in structure and function (apical: cilia, microvilli, secretions; basal: attachment to connective tissue).Naming framework: First word = number of layers (simple vs stratified vs pseudostratified); second word = cell shape (squamous = flat, cuboidal, columnar).Special types: Endothelium (lines blood/lymph vessels), mesothelium (lines serous cavities).Function vs structure examples: Simple squamous for fast gas diffusion (alveoli); simple columnar with microvilli for absorption/secretion (intestine); pseudostratified ciliated for mucus clearance (trachea).Regeneration & cancer: Epithelia regenerate very fast; about ~90% of cancers are epithelial in origin (carcinomas).Microvilli vs cilia: Microvilli = plasma membrane extensions increasing surface area for absorption; cilia = motile projections that move mucus/particles.Topics CoveredEpithelium as a barrierStatement: only crosses epithelium enter the body.Example: Swallowed glass passes through lumen but does not enter body tissues unless epithelium breached.Clinical: Paper cut vs deep cut — bleeding indicates breach past epithelium and potential bacterial entry.Cellularity and extracellular spaceCells are tightly packed with almost no extracellular space in epithelial layers.Contrast: connective tissue has abundant extracellular matrix; epithelium lacks ECM and sits on connective tissue for support.Junctions and attachmentsTight junctions / adhesive junctions / desmosomes glue cells together to prevent leakage and maintain integrity.Hemidesmosomes attach epithelial basal surface to connective tissue to prevent lifting.Polarity: apical vs basalApical surface: free surface; may have cilia, microvilli, or secretory specializations; where function (secretion/absorption/movement) occurs.Basal surface: attaches to connective tissue; provides physical support and nutrient supply because epithelium is avascular.Nutrient source: epithelium obtains oxygen/nutrients by diffusion from the vascular connective tissue (areolar connective tissue with capillaries) beneath.Naming system and shapesFirst word = layers: "simple" = one layer; "stratified" = >1 layer; "pseudo(stratified)" = nuclei at different heights but all cells touch basal lamina.Second word = shape of apical cells: squamous = flat (thin for diffusion), cuboidal, columnar = tall (larger volume for secretion/storage).Combined examples: simple squamous, simple columnar, stratified cuboidal, pseudostratified ciliated columnar.Functional relationships and organ examplesSimple squamous: alveoli — minimal thickness for rapid O2/CO2 exchange.Simple columnar (nonciliated, microvilli): small and large intestine — microvilli massively increase surface area for absorption and secretion (mucus, enzymes).Pseudostratified ciliated columnar: trachea and some large bronchi — cilia move mucus ("ciliary escalator") to trap and clear inhaled particles; fallopian tubes use cilia to move egg.Mesothelium: visceral/parietal layers lining serous cavities (pleura, pericardium) — secretes small amount of serous fluid to reduce friction.Surface specializationsMicrovilli: extensions of the plasma membrane that increase apical surface area; abundant in absorptive epithelia (tons of microvilli in intestine).Cilia: motile, pair-like projections that move mucus or fluid along the epithelial surface (trachea, bronchi, fallopian tube).Regeneration, pathology, and clinical relevanceHigh regeneration rate of epithelia allows rapid repair but increases cell division risk; most cancers (~90%) are epithelial (carcinomas).Chronic irritation increases proliferation and mutation risk: e.g., chronic acid reflux / heartburn → repeated esophageal epithelial damage → increased risk of esophageal cancer.Functional tradeoffs: thin epithelia (simple) allow fast crossing of substances but provide less physical protection; stratified epithelia provide greater protection (uppercase P for emphasis when multiple layers).Pseudostratified vs stratified clarificationPseudostratified: nuclei at different levels create appearance of layers; all cells contact basal surface (not truly stratified).True stratified: cells stack and only basal layer contacts basal lamina; apical cells may be dead (e.g., outer keratinized skin layers).Practical/teaching notes and exam focusInstructor emphasized understanding structure → function instead of rote memorization of locations.Naming rules and visual recognition (apical shape, number of layers, presence of cilia/microvilli) are frequent exam targets.Instructor called out key test points: pseudostratified vs stratified distinction, simple squamous in alveoli, simple columnar in gut, pseudostratified ciliated in respiratory tract, epithelial regeneration and cancer risk.

Study Guide Module 2 MODULE 2 STUDY GUIDE The Integumentary System ⸻ CHAPTER 1: OVERVIEW OF THE INTEGUMENTARY SYSTEM Components of the Integumentary System The integumentary system consists of: * Skin * Hair * Nails * Sweat glands * Sebaceous glands The skin is the largest organ in the body. Functions of the Integumentary System 1. Protection 2. Sensation 3. Thermoregulation 4. Vitamin D synthesis 5. Communication ⸻ CHAPTER 2: LAYERS OF THE SKIN The skin has two major layers: Epidermis * Superficial layer * Keratinized stratified squamous epithelium * Avascular Dermis * Deeper layer * Connective tissue * Contains blood vessels, nerves, glands, and hair follicles Hypodermis * Not technically part of the skin * Also called subcutaneous layer * Contains adipose tissue Functions: * Energy storage * Cushioning * Insulation * Anchoring skin ⸻ CHAPTER 3: EPIDERMIS Cell Types Keratinocytes * Most abundant cells * Produce keratin Melanocytes * Produce melanin * Protect against UV radiation Tactile (Merkel) Cells * Touch receptors Dendritic Cells * Immune defense * Phagocytize pathogens ⸻ EPIDERMAL LAYERS Deep → Superficial Stratum Basale * Deepest layer * Single layer of cuboidal cells * Contains stem cells * Contains melanocytes * Contains tactile cells * Site of mitosis Stratum Spinosum * 8–10 layers thick * Contains dendritic cells * Connected by desmosomes Stratum Granulosum * 3–5 layers * Keratinization begins * Cells flatten * Organelles begin breaking down Stratum Lucidum * Only in thick skin * Palms and soles * Dead transparent cells Stratum Corneum * 15–30 layers * Dead keratinized cells * Protection from abrasion * Prevents dehydration ⸻ THICK VS THIN SKIN Thick Skin Found on: * Palms * Soles Contains: * Stratum lucidum Thin Skin Found everywhere else Does not contain: * Stratum lucidum ⸻ EPIDERMAL WATER BARRIER Located between: * Stratum spinosum * Stratum granulosum Functions: * Waterproofing * Prevents dehydration * Prevents excess water entry Components: 1. Filaggrin 2. Lamellar proteins 3. Lamellar lipids 4. Tight junction proteins ⸻ CHAPTER 4: DERMIS Made of connective tissue. Papillary Layer Contains: * Areolar connective tissue * Dermal papillae * Capillaries * Tactile corpuscles (Meissner corpuscles) Function: * Light touch sensation Reticular Layer Contains: * Dense irregular connective tissue * Hair follicles * Sweat glands * Sebaceous glands * Arrector pili muscles * Lamellated (Pacinian) corpuscles Function: * Deep pressure * Vibration sensation ⸻ DERMAL FIBERS Collagen Provides: * Strength * Support * Water retention Elastin Provides: * Elasticity * Stretching ability ⸻ CHAPTER 5: PIGMENTATION Melanin Produced by: * Melanocytes Functions: * Skin color * UV protection Effects of UV Exposure UV stimulates: * Keratinocytes * Melanocytes Result: * Increased melanin production * Tanning ⸻ Disorders of Pigmentation Albinism Cause: * Lack of melanin production Effects: * Pale skin * Light sensitivity * Increased skin cancer risk Vitiligo Cause: * Loss of melanocyte activity Effects: * White patches on skin ⸻ CHAPTER 6: FUNCTIONS OF THE SKIN Protection Protects against: * Microorganisms * Chemicals * UV radiation * Water loss * Physical trauma Dermicidin: * Antimicrobial substance in sweat ⸻ Sensory Function Skin detects: * Touch * Pain * Temperature * Pressure * Vibration Receptors Meissner Corpuscles * Light touch Pacinian Corpuscles * Deep pressure * Vibration Tactile Cells * Touch Hair Root Plexus * Detects hair movement ⸻ Thermoregulation When Body Is Hot Blood vessels: * Dilate Sweat glands: * Increase secretion Result: * Cooling When Body Is Cold Blood vessels: * Constrict Result: * Conserves heat Can lead to: * Frostbite ⸻ Vitamin D Synthesis UV exposure stimulates vitamin D production. Vitamin D helps: * Calcium absorption * Bone health * Immune function Deficiency causes: Rickets Children Osteomalacia Adults ⸻ Communication Examples: * Facial expressions * Goosebumps * Sweating * Hair patterns ⸻ CHAPTER 7: HAIR Hair Structure Hair Shaft Visible portion Hair Root Embedded portion Hair Follicle Surrounds root Hair Bulb Growth region Hair Matrix Mitotic cells Hair Papilla Blood supply ⸻ Hair Layers 1. Medulla 2. Cortex 3. Cuticle ⸻ Hair Functions * Protection * Thermoregulation * Sensation * Communication ⸻ Hair Growth Average: * 0.3 mm/day Normal loss: * About 50 hairs/day ⸻ Hair Color Determined by: * Melanin Gray hair: * Reduced melanin production ⸻ Arrector Pili Muscle Functions: * Causes goosebumps * Helps retain heat Controlled by: * Sympathetic nervous system ⸻ Alopecia Definition: * Hair loss Pattern baldness: * Hormonal and genetic ⸻ CHAPTER 8: NAILS Functions: * Protection * Support for grasping Structures: * Nail body * Nail root * Nail matrix * Nail bed * Lunula * Cuticle (eponychium) * Hyponychium ⸻ CHAPTER 9: GLANDS Eccrine Sweat Glands Location: * Most of body Functions: * Thermoregulation Secrete: * Water * Salt * Waste products ⸻ Apocrine Sweat Glands Location: * Armpits * Genital regions Characteristics: * Empty into hair follicles * Produce odor after bacterial breakdown ⸻ Sebaceous Glands Produce: * Sebum Functions: * Lubricates skin * Waterproofs skin * Prevents drying * Antibacterial effects ⸻ CHAPTER 10: SKIN CANCER Basal Cell Carcinoma Origin: * Stratum basale Characteristics: * Most common * Least likely to metastasize ⸻ Squamous Cell Carcinoma Origin: * Stratum spinosum Characteristics: * More aggressive * Can metastasize ⸻ Melanoma Origin: * Melanocytes Characteristics: * Most deadly * Highly metastatic ABCDE Rule A = Asymmetry B = Border irregularity C = Color variation D = Diameter > 6 mm E = Evolving ⸻ CHAPTER 11: SKIN DISORDERS Eczema Symptoms: * Dry skin * Itching * Rash * Inflammation Treatment: * Moisturizers * Corticosteroids ⸻ Acne Cause: * Excess sebum * Keratin buildup * Bacterial infection Common locations: * Face * Chest * Back ⸻ CHAPTER 12: WOUND HEALING Steps: 1. Clot Formation Stops bleeding 2. Scab Formation 3. Fibroblast Activity Produces collagen 4. Capillary Growth 5. Epidermal Repair ⸻ CHAPTER 13: BURNS First-Degree Burn Damage: * Epidermis only Symptoms: * Redness * Pain ⸻ Second-Degree Burn Damage: * Epidermis + part of dermis Symptoms: * Blisters * Swelling * Pain ⸻ Third-Degree Burn Damage: * Epidermis * Dermis * Hypodermis Characteristics: * Nerve destruction * Often painless initially * Requires grafting ⸻ Rule of Nines Head and neck = 9% Each arm = 9% Each leg = 18% Trunk = 36% Genitalia = 1% ⸻ CHAPTER 14: SCARS Scar Tissue Produced by: * Fibroblasts Contains: * Collagen Lacks: * Hair follicles * Sweat glands * Sebaceous glands ⸻ Keloid Raised scar due to excessive collagen Atrophic Scar Sunken scar Examples: * Acne scars * Chickenpox scars ⸻ CHAPTER 15: PRESSURE AND FRICTION INJURIES Bedsores Cause: * Prolonged pressure Result: * Reduced blood flow * Tissue death ⸻ Stretch Marks Cause: * Rapid growth * Pregnancy * Weight gain ⸻ Calluses Cause: * Repeated friction Result: * Thickened epidermis ⸻ Corns Specialized calluses ⸻ Blisters Cause: * Friction Result: * Fluid accumulation between skin layers ⸻ CHAPTER 16: AGING AND THE INTEGUMENTARY SYSTEM Changes: Epidermis * Thinner * Slower cell division Dermis * Less collagen * Less elastin * Slower healing Hypodermis * Fat redistribution * Less cushioning Hair * Thinner * Grayer Nails * Slower growth * More brittle Glands * Less sweat * Less sebum Skin * Wrinkles * Sagging * Dryness ⸻ HIGH-YIELD EXAM FACTS Epidermal Layers Basale → Spinosum → Granulosum → Lucidum → Corneum Touch Receptors * Meissner = Light touch * Pacinian = Pressure/Vibration Pigment Cell * Melanocyte Immune Cell * Dendritic Cell Touch Cell * Merkel (Tactile) Cell Cancer Origins * Basal Cell Carcinoma = Stratum Basale * Squamous Cell Carcinoma = Stratum Spinosum * Melanoma = Melanocytes Sweat Glands * Eccrine = Cooling * Apocrine = Odor Burn Depths * 1st = Epidermis * 2nd = Epidermis + Dermis * 3rd = Epidermis + Dermis + Hypodermis Vitamin D Deficiency * Rickets * Osteomalacia This should cover essentially all of the major concepts from the four readings and is the type of material most likely to appear on a Module 2 Anatomy & Physiology exam

DERMOTOMES, MYOTOMES, REFLEX TESTS

Desmosome Junctions

Introduction to Tissues A. Histology=the study of tissues. B. Although studying tissues can be accomplished using a light microscope, studying cell parts often requires an electron microscope and the study of atoms and molecules can only be examined through special imaging techniques and experimental procedures. Types of Tissues A. Despite the fact the body is composed of trillions of cells, there are only about 200 different cell types. These cells in turn produce only four principle tissue types: 1. Epithelial tissues=covers exposed surfaces; lines internal passageways; and produces glandular secretions. 2. Connective tissues=fills internal spaces; provides structural support, and stores energy 3. Muscle tissues=contracts to produce active movements 4. Nervous tissue=conducts electrical impulses; detects, interprets, and responds to stimuli B. Relative contribution of the four tissue types to the overall weight of the adult body. C. Embryonic origins: There are three types of embryonic tissues from which all adult tissues are derived. a. Endoderm=gives rise to the functional linings of the digestive and respiratory tracts as well as to the associated accessory glands and organs (i.e. liver, stomach, pancreas, etc.) b. Mesoderm= gives rise to the components of the skeletal, muscular, and circulatory systems c. Ectoderm= gives rise to the epidermis of skin and all of the components of the nervous system D. Tissue Membranes 1. Mucous Membranes=composed of epithelial tissues. These membranes line body cavities that open to the exterior environment such as those of the digestive tract, respiratory tract, or urogenital tract. In all cases, these are "wet" or moist membranes because of the secretion of mucous. The moisture helps reduce friction and in many cases, facilitates absorption or secretion activities. 2. Serous Membranes=consists of a mesothelium supported by areolar tissue. These are never exposed or connected to the exterior. Serous membranes secrete transudate, or serous fluid. There are three serous membranes that line the ventral body cavity: a. Pleura=lines the chest cavity and surrounds the lungs. b. Pericardium=lines the pericardial cavity and surrounds the heart c. Peritoneum=lines the peritoneal cavity and lines the surfaces of the visceral organs 3. Cutaneous Membranes=made of stratified squamous and areolar tissue reinforced by dense irregular connective tissue. In contrast to mucous and serous membranes, cutaneous membranes are dry, relatively thick, and waterproof. 4. Synovial Membranes=line mobile joint cavities but do not cover the opposing joint surfaces. Secretes synovial fluid. Although the covering of the synovial membrane is often called an epithelium, it differs from true epithelia in four respects: it develops within a connective tissue, no basal lamina is present, gaps of up to 1 mm may separate adjacent cells, and the synovial fluid and capillaries in the underlying connective tissue are continuously exchanging fluid and solutes. Epithelial Tissues A. Functions of Epithelial Tissues 1. Epithelia provide physical protection. Epithelial tissues protect exposed and internal surfaces from abrasion, dehydration, and destruction by chemical or biological agents. 2. Epithelia control permeability. Any substance that enters or leaves the body has to cross an epithelial tissue. Some epithelia are relatively impermeable, whereas others are permeable to compounds as large as proteins. Most are capable of selective absorption or secretion. The epithelial barrier can be regulated and modified in response to various stimuli. For example, a callus forms on your hands when you do rough work for an extended period of time. 3. Epithelia provide sensation. Sensory nerves extensively innervate most epithelia. Specialize epithelial cells can detect changes in the environment and convey information about such changes to the nervous system. 4. Epithelial cells that produce secretions are called glands. Individual gland cells are often scattered among other cell types in an epithelium that may have many other functions. B. Location of Epithelial Tissues 1. Epithelia=forms sheets or layers of cells that line the body tubes, cavities, or coverings of the body surfaces. 2. Glands=formed of epithelial cells with secretory functions. Two types of glands are found in the human body: a. Endocrine glands=secrete hormones (or hormonal precursors) into the interstitial fluid or bloodstream. These glands are ductless. b. Exocrine glands=secretes non-hormonal substances (milk, wax, enzymes, oil, acids, etc.) onto external surfaces or internal passageways (ducts) that connect to the exterior. C. Characteristics of Epithelial Tissues 1. Polarity=epithelial cells possess two structurally and functionally different surfaces: a. Apical surface=free edge which faces the exterior of the body or the lumen of an internal space. b. Basal surface=attached surface which anchors the cells to adjacent tissues. 2. Supported by a basal lamina=also known as the basement membrane, is a complex structure produced by the basal surface of the epithelial cells and the underlying connective tissue. The underlying connective tissue is composed of two things: 3. Cellularity=epithelial cells are extensively interconnected so that they create an effective barrier that behaves as if it were a single cell. a. Occluding junctions=form a barrier that isolates the basolateral surfaces and deeper tissues from the contents of the lumen. At an occluding junction, the attachment is so tight that it prevents the passage of water and solutes between the cells. b. Adhesion belt=locks together the terminal webs of neighboring cells, strengthening the apical region and preventing distortion and leakage at the occluding junctions. It forms a continuous band that encircles cells and binds them together. c. Gap junctions=permits chemical communication that coordinates the activities of adjacent cells. At a gap junction, two cells are held together by interlocking junctional proteins called connexons which serve as channels that form a narrow passageway to let small molecules and ions to pass from cell to cell. d. Desmosomes=provides firm attachment between neighboring cells by interlocking their cytoskeletons. At a desmosome, the opposing plasma membranes are very strong and resist stretching and twisting. Hemidesmosomes attach the basal surface to the basement membrane. e. CAM=cell adhesion molecules; present in the adhesion belt and desmosomes; transmembrane proteins that bind to each other and to extracellular materials. 4. Avascular=epithelial tissues lack blood vessels; all nutrient and waste exchange occurs as a result of diffusion and osmosis from underlying tissues. 5. Highly innervated=epithelial tissues are supplied with many nerve endings 6. Regenerate rapidly=although the exact rate varies from one type of epithelia to another, most epithelial tissues regenerate within days (rather than weeks or years). D. Naming Epithelial Tissues 1. Almost all epithelial tissues possess a two part name where the first part of their name indicates their arrangement (number of layers) while the second part of their name indicates the shape of the cells. 2. Arrangement of epithelial tissues a. Simple=only one layer thick b. Stratified=more than one layer thick c. Pseudostratified= “false layers”; it looks like more than one layer but in fact its only one layer thick 3. Shape of epithelial cells a. Squamous=thin, flat, and somewhat irregular in shape. From the surface, they look like fried eggs lay side by side. In a sectional view, they look like a pancake with a pat of butter (indicating the nucleus). b. Cuboidal=are about as wide as they are tall; resemble hexagonal boxes with the spherical nucleus located in the center of each cell. c. Columnar=are taller than they are wide; resemble rectangles with the elongated nuclei tend to crowd into a narrow band close to the basal lamina. E. Diversity of Epithelial Tissues 1. Simple squamous epithelium a. Description: single layer of flattened cells with a disc-shaped central nuclei and sparse cytoplasm. b. Function: allows passage of materials by diffusion and filtration in sites where protection is not important. Also secretes lubricant. c. Locations: Kidney glomeruli, air sacs of lungs, capillaries, linings of heart and lymphatic system. 2. Stratified squamous epithelium a. Description: thick layers of flattened cells; often keratinized layer and a mitotic layer. b. Function: protects underlying tissues in areas subject to abrasion c. Location: non-keratinized type lines the mouth and vagina; keratinized type forms the epidermis of skin. 3. Simple cuboidal epithelium a. Description: single layer of cube-like cells with large spherical centrally located nuclei. b. Function: secretion and absorption c. Locations: Kidney tubules, ducts and secretory portions of glands, ovary surface 4. Stratified cuboidal epithelium a. Relatively rare in the human body. b. Most common along the ducts of sweat glands, mammary glands, and other exocrine glands. c. DO NOT NEED TO KNOW FOR THE LAB PRACTICAL!! 5. Simple columnar epithelium a. Description: single layer of tall cells with round to oval nuclei; some cells bear cilia; may contain goblet cells that produce mucus; may contain microvilli. b. Function: absorption; secretion of mucus and enzymes; cilia propel substances. c. Location: non-ciliated type lines digestive tract, gallbladder, and ducts from glands; ciliated type lines small bronchi, uterine tubes, and uterus. 6. Stratified columnar epithelium a. Relatively rare in the human body. b. Most often found lining large ducts such as those of the salivary glands and pancreas. c. DO NOT NEED TO KNOW FOR THE LAB PRACTICAL!! 7. Pseudostratified columnar epithelium a. Description: single layer of cells of differing heights so that nuclei are a differing levels; may contain goblet cells and bear cilia. b. Function: secretion, propulsion by ciliary action. c. Location: non-ciliated type lines male reproductive ducts; ciliated type lines much of respiratory tract. 8. Transitional epithelium a. Description: resembles both stratified squamous and stratified cuboidal. Basal cells are cuboidal or columnar; surface cells are dome shaped. b. Function: stretches readily and permits distension. c. Location: Lines uterus, bladder, and urethra F. Glandular Epithelia are Specialized for Secretion 1. Endocrine glands= “ductless” glands that produce hormones. Secrete directly into interstitial fluids or bloodstream. Examples: pituitary gland, adrenal gland, thyroid gland, etc. 2. Exocrine glands=glands possessing ducts. Exocrine glands secret their substance either on the body surfaces or within ducts. They general demonstrates one of two different modes secretion: a. Merocrine=secrete products from secretory vesicles by exocytosis. Most common type. Example: salivary glands of the oral cavity b. Holocrine=accumulate products until the cell ruptures. Destroys the cell and must be replaced by cell division. Example: sebaceous glands of the skin c. Apocrine=products accumulate within the cells then the apex of the cell pinches off packets that contain the secretion. Example: mammary gland of the breast 3. Exocrine glands are unicellular or multicellular. a. Unicellular=goblet cells that produce mucin which mixes with water to form mucus. b. Multicellular=two structural classes: i. Simple=a single duct that does not branch on its way to the secretory cells (examples: gastric glands, sebaceous glands) ii. Compound= duct divides one or more times on its way to the secretory cells (examples: duodenal glands, mammary glands and salivary glands) Connective Tissues: Supports and Protects A. Location of Connective Tissues 1. Most abundant tissue in the body. 2. Never exposed to the outside environment. B. Characteristics of Connective Tissues 1. All types of connective tissue originate from mesenchyme. 2. Connective tissues vary widely in appearance and function but all forms share three basic components: a. Specialized cells=the cells present in each type of connective tissue helps to distinguish the various types from one another. A few of the cells are listed here: i. Fibroblast cells=produce connective tissue proper ii. Chondrocytes=produce cartilage iii. Osteocytes=produce bone iv. Hemocytoblast cells=produce blood b. Extracellular proteins fibers=three primary fibers are produced in connective tissues i. Elastic fibers=slender, straight, and very stretchy. They recoil to their original length after stretching or distortion. ii. Collagen fibers=thick, straight or wavy, and often forms bundles. They are very strong and resist stretching. iii. Reticular fibers=strong fibers that form a branching network or scaffolding c. Ground substance=material that fills the space between cells and surrounds the extracellular fibers. In some connective tissues the ground substance is gel-like while in others it is liquid based and in others it is rigid or calcified. Ground substance and extracellular fibers make up the matrix of connective tissues. 3. Many types of connective tissue are highly vascular and contain sensory receptors that detect pain, pressure, temperature, and other stimuli. C. Functions of Connective Tissues 1. Establish a structural framework for the body. 2. Transport fluids and dissolved materials. 3. Protect delicate organs. 4. Support, surround, and interconnect other types of tissue. 5. Store energy reserves, especially in the form of triglycerides. 6. Defend the body from invading microorganisms. D. Diversity of Connective Tissues 1. Connective Tissue Proper=includes connective tissues with many types of cells and extracellular fibers in a gel-like ground substance. a. Loose Connective Tissues – fibers created a loose, open framework i. Areolar tissue=most common form of connective tissue proper in adults. It is the general packing material in the body. Attaches skin to underlying body parts and is sometimes called the superficial fascia. All of the cell types found in other forms of connective tissue proper can be found in areolar. ii. Adipose tissue=found deep to the skin, especially at the flanks, buttocks, and breasts. It also forms a layer that provides padding within the orbit of the eyes, in the abdominopelvic cavity, and around the kidneys. The distinction between areolar tissue and adipose is the larger number of adipocytes (fat cells). iii. Reticular tissue=found in the liver, kidney, spleen, lymph nodes, and bone marrow, where it forms a tough, flexible network that provides support and resists distortion. In reticular tissue, reticular fibers create a complex supporting network known as a stroma. Fixed macrophages and fibroblasts are present but these cells are seldom visible. DO NOT NEED TO KNOW FOR THE LAB PRACTICAL!! b. Dense Connective Tissues – fibers are densely packed together i. Dense regular=all collagen fibers are oriented parallel to each other providing strength along the axis of the collagen fibers. Found in cords (such as tendons) or sheets (ligaments). Tendons connect muscle to bones. Ligaments connect bones to bones. ii. Dense irregular=collagen fibers are non-parallel forming an interwoven network. These tissues provide strength in many directions and are particularly important in areas subjected to stress from many directions such as the dermis of the skin. iii. Elastic=when elastic fibers outnumber collagen fibers, the tissue has a springy, resilient nature that allows it to tolerate cycles of extension and recoil. This elastic tissue is bound between the vertebrae of the spinal column and the erectile tissues of the penis. DO NOT NEED TO KNOW FOR THE LAB PRACTICAL!! 2. Fluid Connective Tissues=have distinctive populations of cells suspended in a watery matrix that contains dissolved proteins. NOT ON LAB PRACTICAL! a. Blood – flows within the cardiovascular system 3. Supporting Connective Tissues=differ from connective tissue proper in have a less diverse cell population and a matrix containing much more densely packed fibers. Supporting connective tissues protect soft tissues and support the weight of part or all of the body. a. Cartilage – solid, rubbery matrix containing chondrocytes. All cartilage is surrounded by a membrane of connective tissue called the perichondrium. i. Hyaline cartilage=found connecting the ribs to the sternum, covering the articular surfaces of long bones, supporting the respiratory passageways such as the trachea, and forming the tip of the nose and part of the nasal septum. Has an amorphous matrix with few visible fibers. It provides stiff but somewhat flexible support and reduces friction between bony surfaces. ii. Elastic cartilage=found in the ear and epiglottis. Has many more elastic fibers within the matrix and is therefore more flexible. iii. Fibrous cartilage=found within the intervertebral discs, the meniscus of the knee, and pubic symphysis. Has many more collagen fibers within its matrix and is therefore very strong. b. Bone – solid, crystalline matrix containing osteocytes. All bone is surrounded by a membrane of connective tissue called the periosteum. NOT ON LAB PRACTICAL! c. Comparison of cartilage and bone. Muscle Tissue in Motion (discussed in detail in Chapter 10-11) NOT ON LAB PRACTICAL! A. Highly vascularized muscular tissue is comprised of elongated cells (called fibers) containing myofilaments (actin and myosin proteins). 
 B

Cell and Structures Cell vs. Viruses • Cells: Simplest living structures capable of performing all life functions independently. • Viruses: Non-living entities requiring a host cell to replicate and survive. Microscopes • Light Microscope: Uses visible light, magnifies up to 1,000x; resolution limited by wavelength of light. • SEM (Scanning Electron Microscope): Creates detailed 3D images of surfaces; does not show internal structures. • TEM (Transmission Electron Microscope): Produces high-resolution images of internal cellular structures. Magnification and Resolution • Magnification: Enlarges an object’s appearance. • Resolution: Measures the clarity of an image by distinguishing two points as separate. Robert Hooke • Coined the term "cells" after observing cork under a microscope. • Published his findings in Micrographia (1665), advancing the study of cells. Cytology and Biochemistry • Cytology: The study of cell structure and function. • Biochemistry: The study of chemical processes and substances within organisms. Cell Fractionation • A laboratory technique to break apart cells and isolate organelles for detailed study. Size Limitations of Cells • Smaller cells have a higher surface area-to-volume ratio, which is essential for efficient exchange of materials. Prokaryotes vs. Eukaryotes • Prokaryotes: No nucleus or membrane-bound organelles; simpler and smaller (e.g., bacteria). • Eukaryotes: Have a nucleus and membrane-bound organelles; larger and more complex. Cell Structures and Functions • Nucleus: Stores genetic material (DNA). • Plasma Membrane: Protects the cell; regulates material exchange. • Cytosol: Fluid portion of the cytoplasm where cellular processes occur. • Microvilli: Increases surface area for absorption in some animal cells. • Cytoskeleton: ◦ Microfilaments (actin): Provides structural support. ◦ Microtubules: Involved in transport and motility. • Animal Cell-Specific Structures: ◦ Desmosomes: Anchor cells together. ◦ Gap Junctions: Channels that allow communication between cells. ◦ Tight Junctions: Create a watertight seal between cells. • Extracellular Matrix (ECM): Nonliving material outside cells, providing structural and biochemical support. • Plant Cell-Specific Structures: ◦ Plasmodesmata: Channels connecting cytoplasm between plant cells. Cellular Respiration Definition • Process of extracting energy from glucose to produce ATP, the cell's main energy currency. ATP • Made by the enzyme ATP synthase, powered by hydrogen ion (H⁺) movement across the inner mitochondrial membrane. Three Stages of Respiration 1 Glycolysis (Cytoplasm): ◦ Reactants: Glucose. ◦ Products: 2 Pyruvate, 2 ATP (net), and NADH. 2 Krebs Cycle (Mitochondrial Matrix): ◦ Reactant: Acetyl CoA. ◦ Products: CO₂, NADH, FADH₂, and 2 ATP. 3 Electron Transport Chain (ETC) (Inner Mitochondrial Membrane): ◦ Reactants: NADH and FADH₂ (electron carriers). ◦ Products: Water and ~32-34 ATP. Key Points • No oxygen = no Krebs cycle or ETC; only 2 ATP are produced via glycolysis. • Fermentation occurs in anaerobic conditions: ◦ Converts pyruvate into lactic acid (in animals) or ethanol (in yeast). Photosynthesis Overview • Process where plants convert light energy into chemical energy (sugars). • Formula: CO2+H2O→O2+G3PCO_2 + H_2O \rightarrow O_2 + G3PCO2​+H2​O→O2​+G3P. Key Concepts 1 Light Reactions (Thylakoid Membranes): ◦ Products: ATP and NADPH (used in the Calvin Cycle). ◦ Oxygen is produced by Photosystem II. 2 Calvin Cycle (Stroma): ◦ Uses ATP and NADPH to fix carbon dioxide into G3P (a sugar precursor). Photosystems • Photosystem II: Produces oxygen and ATP. • Photosystem I: Produces NADPH. Adaptations • C4 Pathway: Spatial separation of steps to avoid photorespiration. • CAM Pathway: Temporal separation, stomata open at night to reduce water loss. Mitosis and Meiosis Mitosis • Division of a eukaryotic somatic (non-reproductive) cell into two identical diploid cells. • Phases: 1 Prophase: Chromosomes condense; spindle forms. 2 Metaphase: Chromosomes align at the cell's equator. 3 Anaphase: Sister chromatids separate. 4 Telophase: Nuclear envelopes reform. 5 Cytokinesis: Cytoplasm splits into two cells. Meiosis • Specialized cell division in germ cells (ovaries/testes) to produce gametes. • Key Features: ◦ Two divisions produce four genetically unique haploid cells. ◦ Crossing over occurs during Prophase I for genetic diversity. Binary Fission • A simple form of cell division in prokaryotes producing two identical cells. Genetics • Haploid: Single set of chromosomes (e.g., gametes). • Diploid: Two sets of chromosomes (e.g., somatic cells). • Punnett Squares and Pedigrees: Tools to predict genetic inheritance. Cell and Structures Cell vs. Viruses • Cells: Simplest living structures capable of performing all life functions independently. • Viruses: Non-living entities requiring a host cell to replicate and survive. Microscopes • Light Microscope: Uses visible light, magnifies up to 1,000x; resolution limited by wavelength of light. • SEM (Scanning Electron Microscope): Creates detailed 3D images of surfaces; does not show internal structures. • TEM (Transmission Electron Microscope): Produces high-resolution images of internal cellular structures. Magnification and Resolution • Magnification: Enlarges an object’s appearance. • Resolution: Measures the clarity of an image by distinguishing two points as separate. Robert Hooke • Coined the term "cells" after observing cork under a microscope. • Published his findings in Micrographia (1665), advancing the study of cells. Cytology and Biochemistry • Cytology: The study of cell structure and function. • Biochemistry: The study of chemical processes and substances within organisms. Cell Fractionation • A laboratory technique to break apart cells and isolate organelles for detailed study. Size Limitations of Cells • Smaller cells have a higher surface area-to-volume ratio, which is essential for efficient exchange of materials. Prokaryotes vs. Eukaryotes • Prokaryotes: No nucleus or membrane-bound organelles; simpler and smaller (e.g., bacteria). • Eukaryotes: Have a nucleus and membrane-bound organelles; larger and more complex. Cell Structures and Functions • Nucleus: Stores genetic material (DNA). • Plasma Membrane: Protects the cell; regulates material exchange. • Cytosol: Fluid portion of the cytoplasm where cellular processes occur. • Microvilli: Increases surface area for absorption in some animal cells. • Cytoskeleton: ◦ Microfilaments (actin): Provides structural support. ◦ Microtubules: Involved in transport and motility. • Animal Cell-Specific Structures: ◦ Desmosomes: Anchor cells together. ◦ Gap Junctions: Channels that allow communication between cells. ◦ Tight Junctions: Create a watertight seal between cells. • Extracellular Matrix (ECM): Nonliving material outside cells, providing structural and biochemical support. • Plant Cell-Specific Structures: ◦ Plasmodesmata: Channels connecting cytoplasm between plant cells. Cellular Respiration Definition • Process of extracting energy from glucose to produce ATP, the cell's main energy currency. ATP • Made by the enzyme ATP synthase, powered by hydrogen ion (H⁺) movement across the inner mitochondrial membrane. Three Stages of Respiration 1 Glycolysis (Cytoplasm): ◦ Reactants: Glucose. ◦ Products: 2 Pyruvate, 2 ATP (net), and NADH. 2 Krebs Cycle (Mitochondrial Matrix): ◦ Reactant: Acetyl CoA. ◦ Products: CO₂, NADH, FADH₂, and 2 ATP. 3 Electron Transport Chain (ETC) (Inner Mitochondrial Membrane): ◦ Reactants: NADH and FADH₂ (electron carriers). ◦ Products: Water and ~32-34 ATP. Key Points • No oxygen = no Krebs cycle or ETC; only 2 ATP are produced via glycolysis. • Fermentation occurs in anaerobic conditions: ◦ Converts pyruvate into lactic acid (in animals) or ethanol (in yeast). Photosynthesis Overview • Process where plants convert light energy into chemical energy (sugars). • Formula: CO2+H2O→O2+G3PCO_2 + H_2O \rightarrow O_2 + G3PCO2​+H2​O→O2​+G3P. Key Concepts 1 Light Reactions (Thylakoid Membranes): ◦ Products: ATP and NADPH (used in the Calvin Cycle). ◦ Oxygen is produced by Photosystem II. 2 Calvin Cycle (Stroma): ◦ Uses ATP and NADPH to fix carbon dioxide into G3P (a sugar precursor). Photosystems • Photosystem II: Produces oxygen and ATP. • Photosystem I: Produces NADPH. Adaptations • C4 Pathway: Spatial separation of steps to avoid photorespiration. • CAM Pathway: Temporal separation, stomata open at night to reduce water loss. Mitosis and Meiosis Mitosis • Division of a eukaryotic somatic (non-reproductive) cell into two identical diploid cells. • Phases: 1 Prophase: Chromosomes condense; spindle forms. 2 Metaphase: Chromosomes align at the cell's equator. 3 Anaphase: Sister chromatids separate. 4 Telophase: Nuclear envelopes reform. 5 Cytokinesis: Cytoplasm splits into two cells. Meiosis • Specialized cell division in germ cells (ovaries/testes) to produce gametes. • Key Features: ◦ Two divisions produce four genetically unique haploid cells. ◦ Crossing over occurs during Prophase I for genetic diversity. Binary Fission • A simple form of cell division in prokaryotes producing two identical cells. Genetics • Haploid: Single set of chromosomes (e.g., gametes). • Diploid: Two sets of chromosomes (e.g., somatic cells). • Punnett Squares and Pedigrees: Tools to predict genetic inheritance.

Subsection of Unit 2 - Cell Junctions & Epithelial Tissues

dezmosomi

desmosomes, gap junctions, tight junctions

Chapter 19: Cell Junctions and the Extracellular Matrix

Lecture 24 - Desmosomes

plasmodesmata, desmosomes, tight junctions, gap junction