Anatomy Exam II Chapter 3: Histology

Learning Objectives of Anatomy Exam II- (Tuesday, Oct. 25th) These are the learning objectives for Anatomy Exam II. Each objective will require you to go back to your chapter PowerPoints, with respective chapter section readings, class notes and any additional resources for elaboration, context, and details. For best study results, study with the goal of relating information to previous knowledge and seek true understanding , rather than “rote memorizing”. Histology- Chapter 3 (all) 1. Be familiar with the major tissue types and their characteristics. a) Epithelial Tissues b) Connective Tissues c) Nerve (Neural) Tissues d) Muscle Tissues 2. Know the various types of cells found in each type of tissues. 3. Know where in the body the different types of tissues are typically found. 4. What are exocrine glands? 5. What are endocrine glands? 6. From which type of tissue are the Exo and endo glands derived? 7. Be familiar with the types of endocrine glands and the various methods by which they organized.

8. What are the methods of glandular secretion? 9. What are the characteristics of mucous and serous membranes? Where are they found and what do they produce? 10. Be able to distinguish mesothelium and endothelium. A) Epithelial Tissues - are sheets of cells that cover every exposed body surface and line any internal cavities and passageways. Includes Epithelia and Glands a) Ex: surface of the skin, lines the digestive, respiratory, reproductive, & urinary tracts--passageways that communicate with the outside world b) Ex: Internal Epithelia - line the chest cavity, fluid-filled chambers in the brain, eye and inner ear, & inner surfaces of the blood vessels and heart c) CHARACTERISTICS: Cellularity, Polarity, Attachment, Avascularity, Sheets/Layers, Regeneration i. Cellularity - composed of almost entirely of cells bound tightly together by junctions (little to no intercellular space between these cells) ii. Polarity - has Apical Surface (faces the exterior of the body), Basal Surface (an internal space) where epithelium contacts the basement membrane, Lateral Surface (the side) contacts the neighboring epithelial cells. Because of the differing functions of the apical, basal, and lateral surfaces, the organelles and other cytoplasmic structures within epithelial cells are distributed unevenly between the exposed and attached surfaces, a property known as polarity. Polarity occurs whether the epithelium contains a single layer or multiple layers of cells iii. Attachment: The basal surface of a typical epithelium is bound to a thin basement membrane, a complex structure produced by the epithelium and cells of the underlying connective tissue. iv. Avascularity: Epithelia do not contain blood vessels and are therefore avascular (ā-VAS-kū-ler; a , without, + vas , vessel). Because of this, epithelial cells must obtain nutrients by diffusion or absorption across their apical or basal surfaces. v. Sheets or layers: All epithelial tissue is composed of a sheet of cells one or more layers thick.

vi. Regeneration: Stem cells located within the epithelium divide to continually replace surface epithelial cells that are damaged or lost. d) FUNCTIONS OF EPITHELIA: i. Protect Surfaces - protect exposed & internal surfaces from abrasion, dehydration, destruction by chemical or biological agents ii. Control Permeability - any substance that enters or leaves the body has to cross an epithelium. Ex: impermeable, permeable to large substance like protein, selective absorption or secretion, other ex: Calluses that form on hand and feet regulate & modify the barrier. iii. Provide Sensation - sensory nerve innervate (arouse/stimulate a nerve/organ to activate) most epithelia Ex: touch receptors respond to pressure by stimulating sensory nerves iv. Produce Specialized Secretions - Gland Cells produce secretion, substances produced in & discharged from a cell. Unicellular glands - individual cells scattered at other cell types in an epithelium. In glandular Epithelia, most or all of the epithelial cells produce secretions e) Specializations of Epithelial Cells i. The apical and lateral surfaces of epithelial cells are specialized in a variety of ways to perform cellular functions. ii. cells usually show a definite polarity along the axis that extends from the apical surface, where the cell is exposed to an internal or external environment, to the basolateral surfaces, where the epithelium contacts the basement membrane and neighboring epithelial cells. iii. polarity means that intracellular organelles are unevenly distributed, and the apical and basolateral plasma membranes differ in terms of their associated proteins and functions. iv. Most epithelial cells have microvilli, small, finger-shaped projections, on their exposed apical surfaces. Microvilli are especially abundant on epithelial surfaces where absorption and secretion occur, such as in the digestive and urinary tracts. v. Stereocilia are very long microvilli; unlike cilia, they cannot move . Stereocilia are found along portions of the male reproductive tract and on receptor cells of the inner ear. vi. A ciliated epithelium has cilia on its apical surface that usually beat together. 1. Ex: the ciliated epithelium lining the respiratory tract beat in a coordinated fashion to move mucus from the lungs toward the throat. The mucus traps particles and pathogens (disease-causing organisms) and carries them away from the lungs. f) Intercellular Connections: i. Basement Membrane: a layer of filaments and fibers that attach an epithelium to the underlying connective tissue. ii. The superficial portion of the basement membrane consists of the basal lamina, which is secreted by epithelial cells. 1. Functions of Basal Lamina: restricting movement of proteins & other large molecules from connective tissue into the epithelium iii. Deep to the basal lamina is the second layer of the basement membrane, the reticular lamina ( lamina reticularis ), which is secreted by the underlying connective tissue.

1. Contains bundles of coarse protein fibers that anchor the basement membrane to the underlying connective tissue. g) Layers & Shape of Epithelial Cells i. Two types of layering: simple and stratified ii. Three Cell Shapes: squamous, cuboidal, and columnar h) Simple Epithelium - ONE LAYER of cells covering its basement membrane. i. Has same polarity, so nuclei form a row at the same distance from the basement membrane. ii. A single layer of cells CANNOT provide much protection - thin and fragile iii. FOUND: thoracic, abdominal, pelvic cavities, chambers of the heart and ALL BLOOD VESSELS. iv. ALSO FOUND: where secretion, absorption or filtration occurs: lining of intestine and gas exchange surfaces of the lungs - their thin single layer provides an advantage by decreasing the diffusion distance & time needed for materials to pass through the epithelial barrier. i) Stratified Epithelium - TWO OR MORE LAYERS of cells. i. Height & Shape differ from layer to layer ii. Multiple layers of cells - thicker & stronger iii. Occur in areas where mechanical or chemical stresses are severe like: surface of the skin and lining of oral cavity. j) Whether SIMPLE or STRATIFIED - it must REGENERATE & REPLACE its cells over time via division of stem cells, located at/near basement membrane. i. In Simple Epithelium - stem cells are part of exposed epithelial surface ii. In Stratified Epithelium - stem cells are found within the deeper layers of the epithelium k) Squamous Epithelium - cells are thin, flat, & irregular in shape like puzzle pieces i. In a side view the nucleus occupies the thickest portion of each cell & looks flattened, like the cell as a whole. ii. From the surface, the cells look like FRIED EGGS laid side by side. iii. SIMPLE SQUAMOUS EPITHELIUM - most DELICATE epithelium in the body. 1. Found in protected regions where diffusion or other transport take place or where a slick, slippery surface reduces friction 2. Ex: Respiratory Exchange surface (ALVEOLI) of the lungs, Serous membrane lining of Thoracic, Abdominal & Pelvic Cavities, inner surfaces of Circulatory System 3. Mesothelium - Simple squamous epithelium that lines body cavities a) The pleura lining the thoracic cavity and the peritoneum lining the abdominal cavity both contain a superficial mesothelium. 4. Endothelium - Simple squamous epithelium lining the heart and blood vessels iv. STRATIFIED SQUAMOUS EPITHELIUM - cells form a series of layers; occurs where mechanical stresses are severe 1. Protects surface of skin & lining of ORAL CAVITY, throat, Esophagus, Rectum, Vagina, Anus 2. Packed with protein KERATIN - tough, fibrous protein component of Nails, Hair, Calluses, & general integumentary surface

3. NONKERATINIZED or MUCOSAL - resists abrasion but MUST BE KEPT MOIST, or it will dry out and deteriorate; OCCURS in: Oral Cavity, Pharynx, Esophagus, Rectum, Anus, Vagina l) Cuboidal Epithelia - little hexagonal boxes, square at sectional views, nucleus centrally located i. SIMPLE CUBOIDAL EPITHELIA - provide limited protection, found where secretion or absortion takes place 1. Ex: Kidney Tubules ii. STRATIFIED CUBOIDAL EPITHELIA - RARE!!! 1. Found lining the DUCTS of Sweat Glands and MAMMARY GLANDS

m) Columnar Epithelia - Hexagonal in Cross Section; height is greater than in their width; nuclei located w/in the basal portion of the cell i. SIMPLE COLUMNAR EPITHELIA - found where absorption or secretion occurs; provide slight protection 1. Ex: lining of the stomach, intestinal tract, uterine tubes, many excretory ducts ii. STRATIFIED COLUMNAR EPITHELIA - RARE. 1. Occur: pharynx, urethra, anus, few large excretory ducts 2. The epithelium may have two or more layers. If it has more than two layers, only the superficial cells are columnar in shape.

iii. PSEUDOSTRATIFIED CILIATED COLUMNAR EPITHELIUM ( pseudo, fake) - mixture of cell types 1. Because the cells’ nuclei are located at varying distances from the surface, the epithelium looks stratified. 2. All cells rest on the basement membrane, so it is actually a simple epithelium. 3. The surface epithelial cells possess cilia. 4. Lines most of the nasal cavity, trachea, and bronchi and also portions of the male reproductive tract. iv. TRANSITIONAL EPITHELIUM - is a stratified epithelium that can STRETCH w/o damaging the epithelial cells 1. Lines the Renal Pelvis, Ureters, Urinary Bladder 2. In an empty urinary bladder, transitional epithelium seems to have many layers, and its outermost cells are rounded or balloon-shaped cuboidal cells. As the bladder fills and stretches it, transitional epithelium resembles a stratified, nonkeratinized epithelium with two or three layers.

n) Glandular Epithelia - we classify glandular epithelia based on the glands’ secretions, structure, and mechanism/method of secretion. Maybe Exorine or Endocrine Glands i. Exocrine Glands ( exo-, outside) - release their secretion onto an epithelial surface through DUCTS. 1. Ex: Enzymes entering digestive tract, perspiration on the skin, milk produced by mammary glands 2. Three types of Exocrine glands: Serous, mucous, mixed. a) Serous Glands - secrete watery solution that usually contains enzymes like: Salivary amylase in SALIVA b) Mucous Glands - secrete glycoproteins called MUCINS that absorb water to form slippery MUCUS like the mucus in saliva c) Mixed Exocrine Glands - may produce both serous & mucous secretions

ii. Endocrine Glands ( endo-, inside) - DUCTLESS glands that release their secretions by exocytosis directly into the interstitial fluid surrounding the cell - secretions called hormones, diffuse into the blood for distribution to other regions of the body 1. Hormones regulate or coordinate the activities of other tissues, organs, and organ systems o) Structure of the Gland i. Unicellular Glands - mucous cells, individual secretory cells 1. UNICELLULAR EXOCRINE GLANDS - Secrete MUCINS a) Two types of Unicellular Glands: Mucous & Goblet i. Mucous Cells - goblet-shaped, mucus-producing, unicellular glands in digestive & respiratory tracts 1. Found in stomach mucosa, respiratory mucosa, salivary glands ii. Goblet Cells - found in small intestine, large intestine, terminal bronchioles, and conjunctiva ii. Multicellular Glands - include glandular epithelia & clusters of gland cells that produce exocrine or endocrine secretions 1. Secretory Sheet - simplest glandular exocrine gland in which glandular cells dominate the epithelium & release their secretions into an inner compartment 2. Ex: the mucus-secreting cells that line the stomach form a secretory sheet that protects the stomach from acids and enzymes. 3. Occurs: submandibular salivary gland produces mucus & digestive enzymes 4. Two characteristics of Multicellular glands: a) The Shape of Secretory portion of the gland

b) The Branching patter of the duct p) Method of Secretion - Eccrine, Apocrine, Holocrine

11. How does epithelial tissue differ from connective tissue? a) Connective tissues are found throughout the body. Unlike epithelial tissues, connective tissues are never exposed to the environment outside the body. 12. What is mesenchyme? Function? What is a fibroblast? Function? a) Mesenchymal cells (or mesenchymal stem cells ) - are present in many connective tissues. i. These cells respond to local injury or infection by dividing to produce daughter cells that differentiate into fibroblasts, macrophages, or other connective tissue cells. b) Fibroblasts - are one of the two most abundant fixed cells in connective tissue proper and are the only cells always present. These slender, star-shaped cells produce all connective tissue fibers. Each fibroblast manufactures and secretes protein subunits that interact to form large extracellular fibers. In addition, fibroblasts secrete hyaluronan, which makes the ground substance viscous.

13. Know how the three types of cartilages differ with respect to matrix, fibers, appearance and use in the body (use the text for accurate info) a) The matrix of cartilage (a connective tissue w/ a gelatinous matrix & abundance of fibers) is a firm gel that contains complex polysaccharides called chondroitin sulfates (predominant proteoglycans in cartilage, responsible for the gelatinous consistency of the matrix) b) Cartilage cells, or chondrocytes , are the only cells within the cartilage matrix. Chondrocytes live in small chambers known as lacunae (small pit or cavity). Three Types of Cartilages: Hyaline, Elastic, Fibrous 1) Hyaline Cartilage - most common type; matrix contains closely packed collagen fibers; tough & somewhat flexible, this is the weakest type. a) Ex: connections between ribs & sternum, conducting passageways of respiratory tract, covering opposing bone surfaces w/in synovial joints like the shoulder 2) Elastic Cartilage - elastic fibers that make it extremely flexible a) Forms the external flap (auricle) of the external ear b) Epiglottis, auditory canal (airway to the middle ear), & cuneiform cartilage of larynx

3) Fibrous Cartilage - has little ground substance and may lack perichondrium, and the matrix is dominated by collagen fibers a) Lie in areas with high stress: Intervertebral Discs between the spinal vertebrae, between pubic bones of the pelvis, around or w/in a few joints and tendons b) Resists compression, absorbs shocks, & prevents damaging bone-to-bone contact c) Collagen fibers w/in fibrous cartilage follow the stress lines encountered at that particular location and therefore are more regularly arranged than those of hyaline or elastic cartilage d) Cartilages heal slowly and poorly, and damaged fibrous cartilage in joints can interfere with normal movement. 14. What are the four different types of membranes that we look at in human anatomy? Be able to describe each of them. Ex. Synovial, Cutaneous, Serous Membrane - any sheet or partition; layer consisting of epithelium & the underlying connective tissue Four Types of Epithelial Membranes: 1) Mucous Membrane (Mucosa) - forms a barrier that resists the entry of pathogens a) Moist because they are lubricated by mucus or other glandular secretions or by fluids: urine or semen b) Lamina Propria - reticular tissue that underlies a mucous epithelium and forms part of a mucous membrane (areolar tissue component); forms a bridge that connects the epithelium to underlying structures; also supports blood vessels & nerves that supply the epithelium c) Ex: Simple Columnar Epithelium of the Digestive Tract

d) Ex: Stratified Squamous Epithelium of the Oral Cavity e) Ex: Transitional Epithelium found in most Urinary Tract 2) Serous Membrane - line body cavities that lack openings to the exterior; the minimize friction between opposing surfaces. a) Consists of a Mesothelium supported by a thin layer of areolar connective tissue rich in blood and lymphatic vessels b) Three types of Serous Membrane: Pleura, Peritoneum, Pericardium i. Pleura - lines the pleural cavity & covers the lungs ii. Peritoneum - lines the peritoneal cavity & covers the surfaces of the enclosed organs iii. Pericardium - lines the pericardial cavity and covers the heart c) Serous membranes are very thin & attach firmly to the body wall & organs they cover d) PRIMARY FUNCTION: minimize friction between parietal & visceral surfaces e) Serous membranes a permeable, so tissue fluids diffuse onto the exposed surface, keeping it moist and slippery f) Transudate - fluid formed on the surfaces of a serous membrane i. Ex: pleural fluid, peritoneal fluid, pericardial fluid 3) Cutaneous Membrane (skin) - covers the surface of the body a) Consists of keratinized stratified squamous epithelium & underlying layer of areolar connective tissue that is reinforced by a layer of dense connective tissue b) It is thick, waterproof, dry. c) Skins is the first line of defense against environmental pathogens 4) Synovial Membranes - line and lubricate joint cavities a) Joints that permit significant movement are surrounded by a fibrous capsule and contain a joint cavity lined by Synovial Membrane b) Consists of areolar tissue covered by an incomplete superficial layer of squamous or cuboidal cells c) Called an Epithelial Tissue, Synovial membrane lining a joint cavity develops within connective tissue. d) Synovial differs from other epithelial tissues: i. It has no basement membrane ii. Its cellular layer is incomplete, w/ gaps between adjacent cells iii. Its “epithelial cells” derive from macrophages and fibroblasts of the adjacent connective tissue e) Some of the lining cells are phagocytic & secretory f) Phagocytic cells remove cellular debris or pathogens that could disrupt joint function g) Secretory cells regulate the composition of the synovial fluid within the joint cavity h) FUCNTION: Lubricates the cartilages in the joint, distributes oxygen and nutrients & cushion shocks

Mesenchyme - is the first connective tissue to appear in the developing embryo; contains star-shaped cells separated by a matrix that contains very fine protein filaments. Mucoid Connective Tissue - loose connective tissue found in umbilical cord 15. What is fascia? What are the different types of fasciae and where are they found? Fascia - layer or sheet of connective tissue that you can see on gross dissection Three Types of Fascia: Superficial, Deep and Subserous 1) Superficial Fascia (Subcutaneous Layer) - also termed hypodermis a) This layer of loose connective tissue separates the skin from underlying tissues and organs. b) It provides insulation and padding and lets the skin and underlying structures move independently 2) Deep Fascia - consists of dense regular connective tissue. a) Its fiber organization resembles that of plywood because all of the connective tissue fibers in a layer run in same direction, orientation changes from layer to layer b) Structures that helps deep fascia resist forces include: Tough Capsules that surround organs (organs in thoracic & peritoneal cavities), perichondrium around cartilages, periosteum around the bones, connective tissue sheaths of muscle c) Deep fascia of neck & limbs, the INTERMUSCULAR FASCIA, passes between groups of muscles and divide the muscles into compartments that differ functionally and developmentally

d) They’re interwoven. Ex: deep fascia around muscle blends into the tendon, whose fibers blend into the periosteum: creates a strong, fibrous network for the body & ties structural elements together 3) Subserous Fascia - layer of loose connective tissue that lies between the deep fascia and the serous membranes that line body cavities a) Separates the serous membranes from the deep fascia, preventing the movements of muscles and muscular organs from severely distorting the delicate lining Muscle Tissues - powerful contractions that shorten its cells along the longitudinal axis -Possesses organelles & properties distinct from those of other cells -Sarcoplasm - cytoplasm of muscle cell -Sarcolemma - plasma membrane of muscle cell Skeletal Muscle Tissue - large cells a) Muscle Fibers - individual skeletal muscle cells; long and slender b) Multinucleate - each cell contains hundreds of nuclei lying deep to the sarcolemma c) Skeletal Muscle cannot divide, but new muscle fibers can produced through division of d) Myosatellite cells (Satellite Cells) = skeletal muscle tissue can partially repair itself after an injury e) Skeletal muscle is called Striated Voluntary Muscle; contain actin & Myosin contractile filaments; look banded or striated; nervous system provides voluntary control over their activities f) When muscle tissue contracts, it pulls on the bone, and the bone moves

Cardiac Muscle Tissue - found in the heart a) Cardiac Muscle cell is smaller than skeletal muscle fiber and has one centered nucleus b) Intercalated Discs - regions where adjacent cardiocytes interlock & where gap junctions permit electrical coupling between the cells c) Consists of branching network of interconnected muscle cells d) Intercalated discs help channel forces of contraction & gap junctions w/in the intercalateds help coordinate the activities of individual cardiac muscles e) Cannot divide f) Lacks myosatellite cells, damage cardiac muscle tissue CANNOT REGENERATE g) Do not rely of nervous system to start contraction h) Pacemaker cells establish a regular rate of contraction i) Striated Involuntary Muscles

Smooth Muscle Tissue - found in the walls of blood vessels, urinary bladder, layers around respiratory, circulatory, digestive & reproductive tracts a) Small with tapering ends, contains single centered nucleus b) Can divide, can regenerate after an injury c) Has no striations d) It is the only non-striated muscle tissue e) Some contract on their own through action of pacemaker cells f) Others contract when stimulated by the nervous system g) Non-striated Involuntary muscle Nervous Tissue - concentrated in the brain & Spinal Cord Two Basic Types of Cells: Neurons & Neuralgia a) Neurons (Nerve Cells) - transmit electrical impulses along their plasma membrane. b) Neuroglia - supporting cells i. Supporing nervous tissue ii. Regulating the composition of interstitial fluid iii. Providing nutrients to neurons -Neurons are the longest cells in the body -Incapable of dividing; very limited ability to repair after injury -Neuron has a cell body (soma), contains large, nucleus; attaches to dendrites and a single axon. -Dendrites received incoming messages; Axons conduct outgoing messages -It is the length of the axon that can make a neuron so long - also called nerve fibers Integumentary -Chapter 4

1 What are the layers of the epidermis? Epidermis has Five Layers: Beginning at the basal lamina and travelling superficially toward the epithelial surface: Stratum Basale, Stratum, Spinosum, Stratum Granulosum, Stratum Lucidum, Stratum Corneum 1) Stratum Basale - deepest layer; single layer cells firmly attached to the basal lamina which separates the epidermis from the loose connective tissue of the adjacent dermis a) Large stem cells (basal cells) dominate the stratum basale b) Melanocytes are scattered among the basal cells of stratum basale; they have melanin; most abundant in cheeks, forehead, nipples and genital region

c) Albinsim - deficient melanin production d) Merkel cells - skin surfaces that lack hair contain epithelial cells “ merkel cells”; most abundant in fingertips and lips; sensitive to touch 2) Stratum Spinosum - layer of epidermis between basale & granulosum a) Each keratinocyte contains bundles (tonofibrils) of protein filaments that extend from one side of the cell to the other. b) Tonofibrils begin & end at a desmosome that connects the keratinocyte to its neightbors; acts as cross braces, strengthening & supporting the cell junctions c) Interlocking network of desmosomes & tonofibrils ties all the cells in stratum spinosum together d) “Spiny Layer” e) Langerhan cells (dendritic Cells) - Cells in the epithelium of the skin & digestive tract that participate in the immune response by presenting antigens to T cells 3) Stratum Granulosum - most superficial layer of epidermis, cells still possess a nucleus a) Consists of keratinocytes that have moved out of the stratum spinosum. b) Keratinocytes manufacture keratohyalin & keratin c) Increased friction in skin = Callus d) Keratin Ex: Hair & Nails 4) Stratum Lucidum (clear layer) - lack organelles & nuclei, are flattened & densely packed, filled with keratin filaments a) Cells do not stain well 5) Stratum Corneum - most superficial layer of both thick & thin skin. a) Consists of numerous layers of flattened, dead cells that possess a thickened plasma membrane. b) Sheds in large group of sheets rather than individually c) Dry, make surface unsuitable for growth of many microorganisms d) Maintenance of this barrier involves: coating surface with secretions of sebaceous & sweat glands e) Keratinization occurs everywhere on exposed skin surfaces except over the anterior surface of the eyes. f) Water resistant, it is not waterproof g) Insensible Perspiration 2. What type of tissue comprises epidermis? Epidermis - keratinized stratified squamous epithelium that overlies the dermis, a connective tissue region containing glands, hair follicles, and sensory receptors. 3. What is the integumentary system proper? What are the accessory organs? -The Integumentary System proper is the skin. -The skin is the largest organ of the human body! -Your integumentary system is your body's outer layer. -The integument has numerous functions, including physical protection, regulation of body temperature, excretion, secretion, nutrition (through vitamin synthesis), sensation, and immunity. -The Accessory structures of the skin include hair, nails, sweat glands, and sebaceous glands. -These organs and structures are your first line of defense against bacteria and help protect you from injury and sunlight. -Your integumentary system works with other systems in your body to keep it in balance.

4. What is meant by cutaneous membrane? Cutaneous membrane is one of the major component of the integumentary system. Cutaneous membrane is called the SKIN. Skin is the largest organ of the body. Cutaneous Membrane consists of Epidermis & Dermis 5. 6. Know the types of cells that are found in each layer? Also know the general characteristics of each layer and how that layer is important to the epidermis The epidermis of the skin consists of a stratified squamous epithelium. There are four cell types in the epidermis: keratinocytes, melanocytes, Merkel cells, and Langerhans cells. -Keratinocytes (ke-RAT-i-NŌ-sīts) are the most numerous cells within the epidermis. -Melanocytes are the pigment-producing cells in the epidermis. -Merkel cells have a role in detecting sensation. -Langerhans cells (also termed dendritic cells ) are wandering phagocytic cells that are important in the body’s immune response. -Melanocytes, Merkel cells, and Langerhans cells are scattered among keratinocytes. 7. Know the layers of the dermis? Deep to the epidermis is the dermis. The dermis has two major parts: a superficial papillary layer and a deeper reticular layer. 1) Superficial Papillary Layer - the superficial layer of the dermis, a) consists of loose connective tissue. b) provide mechanical attachment for the more superficial epidermis. c) It also contains capillaries and axons of neurons. d) Capillaries are branching blood vessels that supply the epidermis, and axons of sensory neurons monitor epidermal receptors. e) The papillary layer gets its name from the dermal papillae that project between the epidermal ridges 2) Deeper Reticular Layer consists of fibers in an interwoven meshwork of dense irregular connective tissue that surrounds blood vessels, hair follicles, nerves, sweat glands, and sebaceous glands. a) Its name comes from the interwoven arrangement of collagen fiber bundles in this region ( reticulum , a little net). b) Some of the collagen fibers in the reticular layer extend into the papillary layer, tying the two layers together; therefore, the boundary between these layers is not clear. c) Collagen fibers of the reticular layer also extend into the deeper subcutaneous layer. d) The arrangement of these connective tissue fibers in the reticular layer is responsible for the strength, toughness and elasticity of the skin.

8. Know the types of connective tissues found in the dermis? The types of connective tissues found in the dermis are Collagen & Elastin 9. What kind of receptor cells are found in the dermis? Cutaneous Receptors are sensory receptors found in the dermis or epidermis. Cutaneous receptors include mechanoreceptors (pressure or distortion), nociceptors (pain), and thermoreceptors (temperature). 10. Where do we find papillary and reticular layers?

11. Know how fingerprints are formed? a) The epidermal ridges of thick skin fingerprints reveal the pattern of epidermal ridges in thick skin. Dermal ridges form friction ridges, ensuring a secure grip on objects. Dermal ridges also form fingerprints, a unique genetic identifier of an individual. The stratum basale of the epidermis forms dermal ridges (also known as friction ridges ) that extend into the dermis, increasing the area of contact between the two regions. Projections from the dermis toward the epidermis, called dermal papillae (singular, papilla ; “nipple- shaped mound”), extend between adjacent ridges They're essentially folds of the outer layer of skin, the epidermis. The “prints” themselves are the patterns of skin oils or dirt these ridges leave behind on a surface you've touched. Your fingerprints began to form before you were born. 12. What is the function of the hypodermis? The hypodermis has many functions, including: Connection : The hypodermis connects your dermis layer to your muscles and bones. Insulation : The hypodermis insulates your body to protect you from the cold and produces sweat to regulate your body temperature, protecting you from the heat. The hypodermis consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the integument. The hypodermis is the bottom layer of skin in your body. It has many important functions, including storing energy, connecting the dermis layer of your skin to your muscles and bones, insulating your body and protecting your body from harm. As you age, your hypodermis decreases in size, and your skin starts to sag. 13. How do thick skin and thin skin differ? The terms thin and thick skin refer to the relative thickness of the epidermis, not to the thickness of the integument as a whole Most of the body is covered by thin skin , which has only four layers because the stratum lucidum is typically absent. In thin skin, the epidermis is a mere 0.08 mm thick, and the stratum corneum is only a few cell layers deep Thick skin , found only on the palms of the hands and soles of the feet, contains all five layers and may be covered by 30 or more layers of keratinized cells. As a result, the epidermis in these locations is up to six times thicker than the epidermis covering the general body surface

Skin can either be thin or thick. The main difference is the thickness of the epidermis and dermis, which are the top two layers of skin. Thin skin covers most of the body and can vary in thinness, with the thinnest skin covering the eyelids. Thick skin is present on the soles of the feet and palms of the hands. 14. What are the human skin pigments? The brown tones of the skin result from the pigment-producing cells called melanocytes. Melanocytes are scattered among the basal cells of the stratum basale. They have numerous cytoplasmic processes that inject melanin—a black, yellow-brown, or brown pigment—into the basal cells in this layer and into the keratinocytes of more superficial layers. Melanocytes are most abundant in the cheeks, forehead, nipples, and genital region. 15. Be familiar with the types of glands associated with the skin. For ex. Eccrine, Apocrine Mammary. “Glands in the Skin” 1) Sebaceous Glands (oil glands) - produce waxy, oily lipid that coats hair shafts & epidermis a) Sebum - waxy secretion that coats the surfaces of hairs; lubricates & protects the keratin of the hair shaft, conditions the surrounding skin & inhibits the growth of bacteria b) Keratin - tough protein, but DEAD, keratinized cells become dry & brittle once exposed to the environment c) Shampooing removes this natural oily coating, & excessive washing can make hairs stiff & brittle. d) Conditioners reduce structural damage by re-hydrating and coating the hair shaft e) Sebaceous Follicles - large sebaceous glands that communicate directly with the epidermis; never produces hairs; found covering the face, back, chest, nipples, external genitalia 2) Sweat Glands - produces watery solution & perform other special functions a) Two Groups: Apocrine Sweat Glands & Eccrine Sweat Glands b) Both apocrine & Eccrine sweat glands contain Myoepithelial cells, located between gland cells and underlying basal lamina

c) Myoepithelial Cells contractions squeeze the gland & discharge the accumulated secretions d) Apocrine Sweat Glands (PUTOK) - sweat glands that release their secretion into hair follicles in the axillae, around the nipples (areolea), & groin i. They are coiled tubular glands that produce viscous, cloudy, odorous secretion ii. They begin secreting at puberty iii. This sweat is a nutrient source for bacteria, whose growth & breakdown intensify the odor, which may be masked by deodorants iv. May also contain PHEROMONES: chemicals that communicate information to other individuals at a subconscious level e) Eccrine Sweat Glands (merocrine) - smaller than apocrine, do not extend as far into the dermis; i. Palms & soles have the highest numbers ii. Coiled tubular glands that discharge their secretions directly onto the surface of the skin iii. Produce a clear secretion called SWEAT or SENSIBLE PERSPIRATION iv. FUNCTIONS: Thermoregulation, Excretion, Protection

16. Know the accessory structures associated with skin and their components. Accessory structures of the skin include hair, nails, sweat glands, and sebaceous glands. These organs and structures are your first line of defense against bacteria and help protect you from injury and sunlight. 17. Pathology : Skin Cancer 18. Be familiar with which skin cancer is the most dangerous and which is the least dangerous. Skin Cancer - abnormal growth of skin cells caused by exposure to UV radiation, primarily SUNLIGHTS What are the characteristics of skin cancer? Basal Cell Carcinoma - originates in the stratum basale. -Most common skin cancer -Slowest growing -Arises in areas that receive UV exposure -Never metastasize but should still be treated quickly to prevent local spread Squamous Cell Carcinoma - Second most common skin cancer -Uncontrolled growth of abnormal squamous cells in the epidermis -Occur in UV-exposed areas of skin -Tobacco is also a trigger (SMOKING) -can Metastasize to tissues, bones, nearby lymph nodes, cause local disfigurement Malignant Melanoma - develops in melanocytes in the basal layer. -Cancerous melanocytes multiply rapidly -metastasize to distant site -Cause most deaths from skin cancer ABCD test Asymmetry - One half of the spot is unlike the other half Border irregularity - The spot has an irregular, scalloped, or poorly defined border Color variability - The spot has varying colors from one area to the next, such as shades of tan, brown or black, or areas of white, red, or blue. Diameter larger than a pencil eraser. - While melanomas are usually greater than 6 millimeters, or about the size of a pencil erase, when diagnosed, they can be smaller

19. What is the anatomy of a hair follicle? How does hair grow? A) Hairs - project beyond the surface of the skin almost everywhere except sides & soles of the feet, palms of the hands, sides of fingers & toes, lips, portions of external genitalia. a) Hair Follicles - nonliving structures that form in organs; extend deep into the dermis, projecting into underling subcutaneous layer b) Hair Papilla - peg of connective tissue containing capillaries & nerves c) Hair Bulb - consists of epithelial cells that surround the papilla d) Hair Matrix - epithelial layer involved in hair production e) Most hair have inner medulla and outer cortex f) Medulla - contains soft & flexible soft keratin g) Cortex - matrix cells closer to the edge of the developing hair; contain hard keratin h) Hard Keratin - gives hair its stiffness i) Single layer of dead, keratinized cells at the outer surface of the hair overlap & form the CUTICLE that coats the hair j) Cuticle - layer of dead keratinized cells surrounding the shaft of hair k) Hair Root - anchors the hair into the skin l) Hair Shaft - extends from this halfway point to the skin surface, where we see the exposed hair tip m) FOLLICLE STRUCTURE: beginning at the hair cuticle & moving outward, the cells of the follicle walls are organized into the ff: i. Internal Root Sheath - produced by cells at the periphery of the hair matrix ii. External Root Sheath - layer includes all the cell layers found in the superficial epidermis iii. Glassy Membrane - layer is a thickened, specialized basal lamina

20. What is an erector pili muscle? Arrector Pili Muscle - extends from the papillary layer of the dermis to the connective tissue sheath surrounding the hair follicle When stimulated, the arrector pili muscle pulls on the follicle and raises the hair. Arrector Pili Muscle - This is a tiny muscle that attaches to the base of a hair follicle at one end and to dermal tissue on the other end. In order to generate heat when the body is cold, the arrector pili muscles contract all at once, causing the hair to "stand up straight" on the skin. The arrector pili muscle (APM) consists of a small band of smooth muscle that connects the hair follicle to the connective tissue of the basement membrane. 21. What are the 3 different types of hair that grow on a person throughout his/her life? What happens to hair as we age? 1) Lanugo - extremely fine & unpigmented; sheds before birth

2) Vellus Hairs - fine “peach fuzz” hairs found over much of the body surface 3) Terminal Hairs - heavy, more deeply pigmented, curly. Ex: Hairs on your head, eyebrows, eyelashes