BIOL 112 Final Exam Study Package PDF

2024-12-01 Tissue: The Living Fabric Individual body cells speci...

2024-12-01 Tissue: The Living Fabric Individual body cells specialized Studying Human Tissue: Microscopy – Each type performs specific functions that Tissue is fixed maintain homeostasis – Preserved TISSUES Tissues Cut – Groups of cells similar in structure that – Sliced thin enough to transmit light or perform common or related function electrons Histology Stained – Study of tissues – Enhances contrast 1 2 Types of Primary Tissues Cell to Cell Adhesion Nervous tissue: Internal communication Brain Spinal cord Nerves Muscle tissue: Contracts to cause movement Muscles attached to bones (skeletal) Muscles of heart (cardiac) Muscles of walls of hollow organs (smooth) Epithelial tissue: Forms boundaries between different environments, protects, secretes, absorbs, filters Lining of digestive tract organs and other hollow organs Skin surface (epidermis) Connective tissue: Supports, protects, binds other tissues together Bones Tendons Fat and other soft padding tissue 3 4 Defining The ECM: Cell Adhesion Proteins Cell to Cell Adhesion Cells are held together by several different complexes: tight junctions The ‘glue of connective tissue” (discussed in epithelia lecture), adhering junctions, and desmosomes. These junctions consist of integral membrane proteins that contact proteins in neighboring cells and that are linked intracellularly to the cytoskeleton. Adhering junctions are linked to actin filaments and appear to generate tissue specific interactions between cells. They form a belt that runs around the cell. Desmosomes are linked to intermediate filaments and provide increased mechanical support to cells. Desmosomes form a spot on the plasma membrane and found in cells subjected to mechanical stress. Fibronectin Laminin 5 6 1  2024-12-01 How Do Adjacent Cells Connect And Communicate? Cell Communication: Cell-Cell Gaps Animal cells are connected by gap junctions But what we’re REALLY interested in – how do cells physically connect to one Channel proteins in both membranes that line up to form a channel connecting the another? cytosols of neighbouring cells. This is the basis for Gap junctions create gaps that connect animal cells. multicellularity Multicellularity allows for the formation of tissues and organs Gap junctions Membrane proteins from adjacent cells line up to form a channel 7 8 Tight Junctions Tight Junctions Form A Seal Between Neighbouring Cells Results from specialized proteins in the membranes of neighbouring cells Forms a water-tight seal between the two membranes 9 10 Desmosomes Desmosomes Desmosomes are made of proteins that link the cytoskeletons of adjacent cells. Desmosomes are one of the stronger cell- to-cell adhesion types and are found in These proteins bind to each other and to the proteins that anchor cytoskeletal intermediate tissue that experience intense mechanical filaments (usually stretch-resistant, like keratin) stress, such as cardiac muscle tissue, bladder tissue, gastrointestinal mucosa, and epithelia. Desmosomes are composed of desmosome- intermediate filament complexes, which is a network of cadherin proteins, linker proteins and keratin intermediate filaments. 11 12 2  2024-12-01 Adherens An adherens junction is defined as a cell junction whose cytoplasmic face is linked to the actin cytoskeleton. Epithelial Tissue – Coverings & Barriers They can appear as bands encircling the cell (zonula adherens) or as spots of attachment to the extracellular matrix (adhesion plaques). 13 14 Two Major Types Of Epithelia Five Characteristics of Epithelial Tissues 1. Polarity Covering/lining epithelia – outer covering of skin and internal organs, inner linings of internal tubes and cavities 2. Specialized contacts Forms boundaries 3. Supported by connective tissues 4. Avascular, but innervated 5. Can regenerate Glandular epithelia – regions of glands that secrete materials In general, epithelial tissues has the following functions Protection, Absorption, Filtration, Excretion, Secretion, Sensory 15 16 Characteristics of Epithelial Tissue: Polarity Characteristics of Epithelial Tissue: Specialized Contacts Cells have polarity Apical Covering and lining epithelial tissues fit closely All are supported by connective tissue – Apical surface (upper free) exposed to May be smooth & slick together Reticular lamina exterior or cavity Most have microvilli (e.g., brush border of – Form continuous sheets – Deep to basal lamina – Basal surface (lower, attached) intestinal lining) Specialized contacts bind adjacent cells – Network of collagen fibers – Both surfaces differ in structure and – Increase surface area – Lateral contacts Basement membrane function Some have cilia (e.g., lining of trachea) Tight junctions – Basal lamina + reticular lamina Basal Desmosomes – Reinforces epithelial sheet Noncellular basal lamina – Resists stretching and tearing – Glycoprotein and collagen fibers lies – Defines epithelial boundary adjacent to basal surface – Adhesive sheet – Selective filter – Scaffolding for cell migration in wound repair 17 18 3  2024-12-01 Characteristics of Epithelial Tissue: Regeneration Characteristics of Epithelial Tissue: Avascular but Innervated High regenerative capacity No blood vessels in epithelial tissue – Must be nourished by diffusion from Stimulated by loss of apical-basal polarity and lateral contacts underlying connective tissues – Some exposed to friction – Some exposed to hostile substances Is supplied by nerve fibers If adequate nutrients can replace lost cells by cell division 19 20 Characteristics of Epithelial Tissue: Connective Tissue Support Hemidesmosomes Anchor Epithelia To Their Basement Membranes All are supported by connective tissue Reticular lamina – Deep to basal lamina – Network of collagen fibers Basement membrane – Basal lamina + reticular lamina – Reinforces epithelial sheet – Resists stretching and tearing – Defines epithelial boundary 21 22 Classification of Epithelia Classification of Epithelia All epithelial tissues have two names Absorption Secretion Filtration When classifying epithelium, one must always – One indicates number of cell layers Very thin describe the number of layers and then the shape of the cells making them up. Simple epithelia = single layer of cells Stratified epithelia = two or more layers of cells – Shape can change in different layers – One indicates shape of cells Squamous (scale-like, flat nucleus) Cuboidal (nucleus normal) Columnar (nucleus elongated) In stratified epithelia, epithelia classified by cell shape in apical layer 23 24 4  2024-12-01 Simple Epithelial Tissues Stratified Epithelial Tissues Simple Stratified – A single layer of cells with every cell in direct contact with the Two or more cell layers basement membrane that separates it from the underlying connective tissue. Regenerate from below – In general, it is found where absorption and filtration occur. – Basal cells divide, cells migrate to surface – The thinness of the epithelial barrier facilitates these processes. More durable than simple epithelia Protection is major role 25 26 Covering and Lining Epithelia: Simple Squamous Epithelium Simple squamous epithelium: This type of epithelium typically lines blood vessels and body cavities and regulates the passage of substances into the underlying tissue. 27 28 Covering and Lining Epithelia: Simple Cuboidal Epithelium Simple Columnar Epithelium Simple cuboidal epithelium is composed Simple columnar epithelium is a single layer of a single layer of cells that have a of columnar epithelial cells which are tall and relatively large surface area. slender with oval-shaped nuclei located in the basal region, attached to the basement membrane. This allows them to function in absorption and secretion of substances like water and salt in the kidneys and In humans, simple columnar epithelium lines hormones and other substances most organs of the digestive tract including produced by glands. the stomach, and intestines. 29 30 5  2024-12-01 31 32 Covering and Lining Epithelia: Ciliated Simple Columnar Covering and Lining Epithelia: Nonciliated Simple Columnar Epithelium Epithelium Mucus in goblet cell Microvilli Bronchioles, sinuses, spinal Lumen of jejunum column lining, brain ventricles Small intestine Nucleus of absorptive cell LM 1500x Nucleus of goblet cell Nonciliated simple columnar Basement membrane epithelium Connective tissue LM 500x Sectional view of nonciliated simple columnar epithelium of lining of jejunum of small intestine 33 34 Covering and Lining Epithelia: Pseudostratified Columnar Epithelium Mucus in Cilia Lumen of goblet cell trachea Cilia LM 630x Pseudostratified Trachea ciliated Nucleus of ciliated columnar cell columnar epithelium Nucleus of goblet cell Nucleus of basal cell Connective tissue LM 400x LM 630x Sectional view of pseudostratified columnar epithelium of trachea Basal cell Other egs: non-ciliated types in large ducts of glands, lining of male reproductive tract 35 36 6  2024-12-01 Covering and Lining Epithelia: Transitional Epithelium Urinary bladder Rounded surface Lumen of urinary bladder cell in relaxed state Nucleus of transitional cell LM 630x Transitional epithelium Connective tissue LM 400x Sectional view of transitional epithelium of urinary bladder in relaxed (empty) state 37 38 Covering and Lining Epithelia: Stratified Squamous Epithelium Non-Keratinized Keratinized Egs. Lining of upper digestive system, Egs. Epidermis vagina, pharynx 39 40 Stratified Cuboidal & Columnar Epithelium Covering and Lining Epithelia: Stratified Cuboidal Epithelium Esophagus Squamous cells are often configured such that they are simple or stratified. Cuboidal and columnar cells are usually simple. Lumen of duct LM 640x Stratified Cuboidal Nuclei of stratified – Quite rare cuboidal cells – Found in some sweat and mammary glands Nucleus of – Typically two cell layers thick cuboidal cell Lumen of duct Stratified Columnar Stratified cuboidal – Limited distribution in body epithelium LM 380x – Small amounts in pharynx, male urethra, and lining some glandular ducts Sectional view of stratified cuboidal epithelium Connective tissue – Also occurs at transition areas between two other types of epithelia of the duct of an esophageal gland – Only apical layer columnar Egs: sweat glands, esophageal glands, male urethra 41 42 7  2024-12-01 Covering and Lining Epithelia: Stratified Columnar Epithelium Covering and Lining Membranes Composed of at least two primary tissue types Lumen of pharynx – An epithelium bound to underlying connective tissue proper Nucleus of stratified – Are simple organs columnar cell Pharynx Three types – Cutaneous membranes – Mucous membranes – Serous membranes LM 630x Stratified columnar epithelium Connective tissue LM 400x Sectional view of stratified columnar epithelium of lining of pharynx Egs: urethra, some glands, conjunctiva of eye 43 44 Cutaneous (Skin) & Mucous Membranes Serous Membranes Skin (Cutaneous) Serosae—found in closed ventral body cavity – Keratinized stratified squamous epithelium (epidermis) attached to a thick layer of connective tissue (dermis) Simple squamous epithelium (mesothelium) – Dry membrane resting on thin areolar connective tissue Mucosa (Mucosae) Parietal serosae line internal body cavity walls – indicates location not cell composition Line body cavities open to the exterior (e.g., Digestive, respiratory, Visceral serosae cover internal organs urogenital tracts) – Moist membranes bathed by secretions (or urine) Serous fluid between layers – Epithelial sheet lies over layer of connective tissue called lamina propria Moist membranes – May secrete mucus Pleurae, pericardium, peritoneum 45 46 Glandular Epithelia Gland – One or more cells that makes and secretes an aqueous fluid called a secretion Classified by – Site of product release—endocrine or exocrine Epithelial Tissue – Glandular Tissue – Relative number of cells forming the gland unicellular (e.g., goblet cells) or multicellular 47 48 8  2024-12-01 Glands Endocrine Glands Ductless glands – Secretions not released Organs that produce a compound and secrete into a duct it somewhere 2 types: Secrete (by exocytosis) 1. Endocrine – substance released into hormones that travel through bloodstream (multicellular) lymph or blood to their 2. Exocrine – substance release into body specific target organs cavity or outer surface of body (unicellular or multicellular) Target organs respond in some characteristic way 49 50 Exocrine Glands Unicellular Exocrine Glands Secretions released onto body The only important unicellular glands surfaces (skin) or into body are mucous cells and goblet cells cavities Found in epithelial linings of More numerous than intestinal and respiratory tracts endocrine glands All produce mucin Secrete products into ducts – Dissolves in water to form mucus Slimy protective, lubricating Examples include mucous, coating sweat, oil, and salivary glands 51 52 Multicellular Exocrine Glands Formation of Multicellular Exocrine and Endocrine Glands Multicellular exocrine glands are composed of a duct and a secretory unit Usually surrounded by supportive connective tissue – Supplies blood and nerve fibers – Extends into and divides gland into lobes Classification by Structure and Type of Secretion – Structure Simple glands (unbranced duct) or compound glands (branched duct) Cells tubular, alveolar, or tubuloalveolal 53 54 9  2024-12-01 Classification of Multicellular Glands Classification of Multicellular Glands Simple duct structure Compound duct structure (duct does not branch) (duct branches) Type of secretion Merocrine – most – secrete products by exocytosis as produced Tubular secretory structure Holocrine – accumulate products within then Simple branched tubular Simple tubular Example Intestinal glands Example rupture Compound tubular Stomach (gastric) glands Example Duodenal glands of small intestine Apocrine – accumulates products within but only apex ruptures Alveolar secretory structure Simple alveolar Simple branched alveolar Compound alveolar Compound Example Example Example tubuloalveolar No important Sebaceous (oil) glands example in humans Mammary glands Example Salivary glands Surface epithelium Duct Secretory epithelium 55 56 Connective Tissue Most abundant and widely distributed of Four main classes primary tissues – Connective tissue proper – Cartilage Extremely diverse in terms of cellular – Bone structure and function Connective Tissue – Blood Common embryological origin (mesenchyme) ECM is far more prominent than in other tissues 57 58 Functions & Characteristics of Connective Tissue Structural Elements of Connective Tissue Three elements Functions: – Ground substance – Binding and support, protecting, Insulating, Storing reserve fuel, Transporting substances (blood) – Fibers – Cells Three characteristics make connective tissues different from other primary tissues – Have mesenchyme (an embryonic tissue) as their common tissue of origin Composition and arrangement varies in different connective tissues – Have varying degrees of vascularity (blood vessels) – Have extracellular matrix Connective tissue not composed mainly of cells 59 60 10  2024-12-01 Connective Tissue Cell Types: Cells "Blast" cells Fibroblasts – Immature form; mitotically active; secrete ground substance and fibers Mast Cells – Fibroblasts in connective tissue proper Macrophages – Chondroblasts in cartilage Adipocytes – Osteoblasts in bone – Hematopoietic stem cells in bone marrow Plasma Cells "Cyte" cells White Blood Cells – Mature form; maintain matrix – Chondrocytes in cartilage – Osteocytes in bone 61 62 Ground Substance Ground Substance Of Connective Tissues Unstructured material that fills space between cells – Medium through which solutes diffuse between blood capillaries and cells Proteoglycans (with Glycosaminoglycan – GAG – chains) Components – Interstitial fluid – Cell adhesion proteins ("glue" for attachment) – Proteoglycans The ‘Big 2’ GAGs: Hyaluronic acid and chindroitin sulfate 63 64 Animal Cells – The Extracellular Matrix (ECM) The Role Of The Extracellular Layer Cell in connective tissue Spaces in between collagen fibrils filled with a gelatinous polysaccharide Steel rods (the “fibers”) resist tension Concrete (the “ground substance”) resists compression Collagen fibrils Collagen fibrils Each collagen fibril is running lengthwise in cross section composed of many collagen molecules 65 66 11  2024-12-01 All ECM In The Body Is Connected To The Cytoskeleton Connective Tissue Fibers Gel-forming Three types of fibers provide support polysaccharides – Collagen Strongest and most abundant type Tough; provides high tensile strength Collagen ECM – Elastic fibers Fibronectin Networks of long, thin, elastin fibers that allow for stretch and recoil Integrin – Reticular Plasma Short, fine, highly branched collagenous fibers membrane (different chemistry and form than collagen fibers) Cytoskeleton Branch, forming networks that offer more "give" Actin filament 67 68 The Extracellular Matrix (ECM) Fibres of Connective Tissue ECM Collagen, the most common ECM protein fiber, is more elastic than cellulose and forms a 1. Collagen flexible extracellular layer. Collagen molecules are made of three chains that wind around each other. 3 chains Collagen molecule Tensile strength 69 70 Fibres of Connective Tissue ECM Fibres of Connective Tissue ECM 1. Collagen Fibers Collagen fibers form the extracellular framework of all tissues and are essential for 2. Elastic Fibres (protein: elastin) tensile strength. The collagen molecules in these fibers are synthesized as larger precursor proteins, known as procollagens, from which large propeptide domains are enzymatically cleaved en bloc. 71 72 12  2024-12-01 Fibres of Connective Tissue ECM Types of Connective Tissues: Connective Tissue Proper All connective tissues except bone, cartilage and blood 3. Reticular Fibres Two subclasses – Loose connective tissues Areolar Adipose Reticular – Dense connective tissues (also called fibrous connective tissues) Dense regular Dense irregular Elastic 73 74 Other Cell Types in Connective Tissues Areolar Connective Tissue Fat cells – Store nutrients Support and bind other tissues – Universal packing material between White blood cells other tissues – Neutrophils, eosinophils, lymphocytes Most widely distributed – Tissue response to injury Provide reservoir of water and salts Defend against infection Mast cells Store nutrients as fat – Initiate local inflammatory response Fibroblasts against foreign microorganisms they detect Loose arrangement of fibers Ground substance Macrophages When inflamed soaks up fluid  edema – Phagocytic cells that "eat" dead cells, microorganisms; function in immune system 75 76 Adipose Tissue White fat – Similar to areolar but greater nutrient storage – Cell is adipocyte Stores nutrients – Scanty matrix – Richly vascularized – Shock absorption, insulation, energy storage Brown fat – Use lipid fuels to heat bloodstream not to produce ATP 77 78 13  2024-12-01 Groups Of Adipose Cells Are Kept Together By Collagen Fibers And Collagen Sheets 79 80 Groups Of Adipose Cells Are Kept Together By Collagen Fibers Groups Of Adipose Cells Are Kept Together By Collagen Fibers And Collagen Sheets And Collagen Sheets 81 82 Reticular Connective Tissue Reticular connective tissue resembles areolar connective tissue, but the only fibers in its matrix are reticular fibers, which form a delicate network along which fibroblasts called reticular cells lie scattered. Although reticular fibers are widely distributed in the body, reticular tissue is limited to certain sites. 83 84 14  2024-12-01 Dense Regular Connective Tissue Dense regular connective tissue belongs to the category of connective tissue proper. It is composed of fibroblasts, protein fibers (collagen and elastin), and a viscous ground substance. There are two types of dense regular connective tissue: dense collagen connective tissue and dense elastin connective tissue. 85 86 Dense Irregular Connective Tissue Dense irregular connective tissue has fibers that are not arranged in parallel bundles as in dense regular connective tissue. Dense irregular connective tissue consists of mostly collagen fibers. It has less ground substance than loose connective tissue. 87 88 Elastic Connective Tissue (Dense) Elastic connective tissue is a type of dense connective tissue. They provide tensile strength and resistance to stretching. They contain both elastin and collagen fibres called fibroblasts. 89 90 15  2024-12-01 Connective Tissue Connective Tissue 91 92 Skin (Integument) Consists of two distinct regions Epidermis—superficial region Epithelial tissue Dermis—underlies epidermis Mostly fibrous connective tissue INTEGUMENTARY SYSTEM Hypodermis (superficial fascia) Subcutaneous layer deep to skin Not part of skin but shares some functions Mostly adipose tissue that absorbs shock & insulates Anchors skin to underlying structures – mostly muscles 93 94 The Skin And SubQ Layer Structure of Skin Skin consists of two distinct regions: – Epidermis: superficial region Consists of epithelial tissue and is avascular – Dermis: underlies epidermis Mostly fibrous connective tissue, vascular – Hypodermis (superficial fascia) Subcutaneous layer deep to skin Not part of skin but shares some functions Mostly adipose tissue that absorbs shock and insulates Anchors skin to underlying structures: mostly muscles 95 96 16  2024-12-01 Epidermis Keratinized stratified squamous epithelium Four or five distinct layers Stratum basale (germinativum) Stratum spinosum Stratum granulosum Epidermis Stratum lucidum (only in thick skin) Stratum corneum Four cell types Keratinocytes Melanocytes Dendritic (Langerhans) cells Tactile (Merkel) cells 97 98 Cells of the Epidermis: Four Cell Types of Epidermis 1. Keratinocytes 3. Dendritic (Langerhans) cells – Produce fibrous keratin (protein that gives – Star-shaped macrophages that patrol deep skin its protective properties) epidermis – Major cells of epidermis Are key activators of immune system – Tightly connected by desmosomes – Millions slough off every day 4. Tactile (Merkel) cells 2. Melanocytes – Sensory receptors that sense touch – Spider-shaped cells located in deepest epidermis – Produce pigment melanin, which is packaged into melanosomes Melanosomes are transferred to keratinocytes, where they protect nucleus from UV damage 99 100 Four Principal Cell Types In Epidermis Layers of the Epidermis 1. Stratum basale (basal layer) – Deepest of all epidermal layers (base layer) – Layer that is firmly attached to dermis – Consists of a single row of stem cells that actively divide (mitotic), producing two daughter cells each time One daughter cell journeys from basal layer to surface, taking 25–45 days to reach surface – Cell dies as it moves toward surface Other daughter cell remains in stratum basale as stem cell – Layer also known as stratum germinativum because of active mitosis – 10–25% of layer also composed of melanocytes 101 102 17  2024-12-01 Cell Differentiation in Epidermis Layers of the Epidermis Cells change from stratum basale to stratum corneum 2. Stratum spinosum (prickly layer) – Several cell layers thick – Cells contain weblike system of intermediate prekeratin filaments attached to desmosomes Allows them to resist tension and pulling Accomplished by specialized form of – Keratinocytes in this layer appear spikey, so they are called prickle cells apoptosis – Scattered among keratinocytes are abundant melanosomes and dendritic cells Controlled cellular suicide Nucleus and organelles break down Plasma membrane thickens Allows cells to slough off as dandruff and dander Shed ~ 50,000 cells every minute 103 104 Layers of the Epidermis Layers of the Epidermis 3. Stratum granulosum (granular layer) 4. Stratum lucidum (clear layer) – Four to six cells thick, but cells are flattened, so layer is thin – Found only in thick skin – Cell appearance changes – Consists of thin, translucent Cells flatten, nuclei and organelles disintegrate band of two to three rows of Keratinization begins clear, flat, dead keratinocytes – Cells accumulate keratohyaline granules that help form keratin fibers in upper layers – Lies superficial to the stratum granulosum Cells also accumulate lamellar granules, a water-resistant glycolipid that slows water loss – Cells above this layer die Too far from dermal capillaries to survive 105 106 Layers of the Epidermis Layers of the Dermis: Papillary Layer 5. Stratum corneum (horny layer) Areolar connective tissue with – 20–30 rows of flat, anucleated, collagen and elastic fibers and keratinized dead cells blood vessels – Accounts for three-quarters of epidermal thickness Loose tissue – Though dead, cells still function to: Phagocytes can patrol for Protect deeper cells from the microorganisms environment Prevent water loss Dermal papillae Protect from abrasion and Superficial peglike penetration projections Act as a barrier against biological, chemical, and physical assaults 107 108 18  2024-12-01 Cutaneous Sensations Dermis Strong, flexible connective tissue Cells Fibroblasts, macrophages, and occasionally mast cells and white blood cells Fibers in matrix bind body together "Hide" used to make leather Contains nerve fibers; blood and lymphatic vessels Contains epidermal hair follicles; oil and sweat glands Two layers Papillary Reticular 109 110 Light Micrograph of the Papillary Layer Dermis Superficial layer of areolar connective tissue consisting of loose, interlacing collagen and elastic fibers and blood vessels Strong, flexible connective tissue Loose fibers allow phagocytes to patrol for Cells include fibroblasts, macrophages, and microorganisms occasionally mast cells and white blood cells Fibers in matrix bind body together Dermal papillae: superficial region of dermis that Makes up the “hide” that is used to make sends fingerlike projections up into epidermis leather – Projections contain: Contains nerves, blood vessels, and Capillary loops lymphatic vessels Free nerve endings Contains epidermal hair follicles, oil glands, and sweat glands Touch receptors (tactile corpuscles, also called Meissner’s corpuscles) 111 112 Dermal Papillae Reticular Layer ~80% of dermal thickness Dense fibrous connective tissue In thick skin lie atop dermal ridges that cause Elastic fibers provide stretch-recoil properties epidermal ridges Collectively ridges called friction ridges Enhance gripping ability Collagen fibers Contribute to sense of touch Provide strength and resiliency Pattern is fingerprints Bind water Cleavage lines because most collagen fibers parallel to skin surface Externally invisible Important to surgeons Incisions parallel to cleavage lines gap less and heal more readily 113 114 19  2024-12-01 Reticular Layer Other Skin Markings Striae Silvery-white scars "Stretch marks" Extreme stretching causes dermal tears Blister From acute, short-term trauma Fluid-filled pocket that separates epidermal and dermal layers 115 116 Mechanoreceptors (Nerve Endings) in the Skin: Corpuscles Tactile (Meissner’s) Corpuscles Bulbous ( Ruffini) Corpuscles Found in the upper dermis Found deeper in the dermis Sense light touch Sense stretch Fast adapting Can also detect warmth Slow adapting Lamellar (Pancinian) Corpuscles Glands Vibration and deep, transient pressure Merkel Corpuscles Found in upper layers of the skin near the dermis Sense touch 117 118 Skin Appendages: Cutaneous Glands Sebaceous (Oil) Glands Widely distributed Not in thick skin of palms and soles Most develop from hair follicles and secrete into hair follicles Relatively inactive until puberty Stimulated by hormones, especially androgens Secrete sebum Oily holocrine secretion Bactericidal Softens hair and skin 119 120 20  2024-12-01 Clinical – Homeostatic Imbalance: Acne Clinical – Homeostatic Imbalance Acne is usually an infectious inflammation of the sebaceous glands, resulting in pimples (pustules or cysts) – Associated with Propionibacterium acne infection Acne is usually an infectious inflammation of Whiteheads are blocked sebaceous glands the sebaceous glands, resulting in pimples – If secretion is oxidized, whitehead becomes a blackhead (pustules or cysts) Associated with Propionibacterium acne infection Overactive sebaceous glands in infants can lead to seborrhea, known as “cradle cap” – Begins as pink, raised lesions on scalp that turn yellow/brown and flake off 121 122 Clinical – Homeostatic Imbalance: Cradle Cap (Seborrhea) in a Newborn Sweat Glands 123 124 Apocrine Sweat Glands Sweat Glands Also called sudoriferous glands Confined to axillary and anogenital areas All skin surfaces except nipples and parts of Secrete viscous milky or yellowish sweat that external genitalia contains fatty substances and proteins ~3 million per person Bacteria break down sweat, leading to body odor Larger than eccrine sweat glands with ducts emptying into hair follicles Two main types Begin functioning at puberty Eccrine (merocrine) sweat glands Function unknown but may act as sexual scent Apocrine sweat glands gland Modified apocrine glands Contain myoepithelial cells Ceruminous glands: lining of external ear Contract upon nervous system canal; secrete cerumen (earwax) stimulation to force sweat into ducts Mammary glands: secrete milk 125 126 21  2024-12-01 Eccrine (Merocrine) Sweat Glands Summary of Cutaneous Glands Most numerous Abundant on palms, soles, and forehead Ducts connect to pores Function in thermoregulation Regulated by sympathetic nervous system Their secretion is sweat 99% water, salts, vitamin c, antibodies, dermcidin (microbe-killing peptide), metabolic wastes 127 128 The Various Types of Glands Sebaceous Glands 1. Sebaceous Glands The skin contains several types of glands, – Function: each with unique functions. Produce and secrete sebum, an oily substance that lubricates the skin and hair, and provides some antibacterial protection. Here are all the types of glands found in – Location: the skin: Distributed throughout most of the body but are most abundant on the face, scalp, chest, – 1. Sebaceous glands (oil glands) and back. They are usually associated with hair follicles but can also exist independently. – 2. Eccrine sweat glands (for – Secretion Type: thermoregulation) Holocrine secretion – cells accumulate sebum and eventually rupture to release it. – 3. Apocrine sweat glands (associated with hair follicles and scent) – 4. Ceruminous glands (earwax production) – 5. Mammary glands (milk production) 129 130 Mammary Glands Summary of Glands - **Function**: Specialized sweat glands that 1. Sebaceous glands (oil glands) produce milk to nourish infants. 2. Eccrine sweat glands (for thermoregulation) - **Location**: Found within the breast tissue. 3. Apocrine sweat glands (associated with hair - **Secretion Type**: Considered modified follicles and scent) apocrine glands, their secretory activity is primarily 4. Ceruminous glands (earwax production) regulated by hormonal changes, such as those 5. Mammary glands (milk production) during pregnancy and lactation. Each gland plays a crucial role in protecting, ### **Summary** lubricating, and maintaining the homeostasis of the The skin houses: body. 1. **Sebaceous glands** (oil glands) 2. **Eccrine sweat glands** (for thermoregulation) 3. **Apocrine sweat glands** (associated with hair follicles and scent) 4. **Ceruminous glands** (earwax production) 131 132 22  2024-12-01 HORMONES & THE ENDOCRINE SYSTEM Endocrine System: Overview Acts with nervous system to coordinate and integrate activity of body cells Influences metabolic activities via hormones transported in blood Response slower but longer lasting than nervous system Endocrinology – Study of hormones and endocrine organs Controls and Integrates: – Reproduction, growth and development, maintenance of electrolyte, water, and nutrient balance of blood, regulation of cellular metabolism and energy balance, mobilization of body defenses 133 134 Endocrine System: Overview Chemical Messengers Exocrine Glands Autocrines: chemicals that exert effects on same cells that secrete them – Non-hormonal substances (sweat, Paracrines: locally acting chemicals that affect cells other than those that secrete them saliva) – Autocrines and paracrines are local chemical messengers; not considered part of – Have ducts to carry secretion to endocrine system membrane surface