Tissues -four primary tissue types: 1. Epithelial 2. Connective 3. Muscle 4. Neural

Epithelial Tissue = lining epithelium & glands multiple functions of epithelial tissues: protection - from dehydration, pathogens synthesis – e.g. vitamin D 3. regulation - e.g. body temperature 4. excretion - e.g. waste 5. immune response 6. control of permeability – every substance must cross an epithelial membrane first 7. sensitivity – epithelial membranes are well-innervated lining epithelium = line body surfaces and cavities glandular epithelium = secretion

Epithelial characteristics Cellularity Polarity Attachment to each other to connective tissue Avascularity Regeneration

Epithelial characteristics 1. Cellularity: composed almost entirely of cells held together by cell junctions -very little extracellular matrix 2. Polarity: possesses an exposed surface the faces the exterior of the body - apical face -also has an attached base which is anchored to other tissues - basal face -the organelles are not uniformly distributed

Epithelial characteristics Epithelial characteristics 3. Attachment: attached to underlying tissues via the basement membrane -BM is produced by the basal surface of the cells & connective tissue -the BM is comprised of two layers a. closest to epithelial cell = basal lamina (glycoproteins, laminin and actin) -acts as a barrier to transport b. furthest from the epithelial cell = reticular lamina -collagen IV bundles produced by the underlying connective tissue cells -provides strength

Epithelial characteristics Epithelial characteristics 1. Tight junctions: lipid portions of PMs are bound together by interlocking membrane proteins -very tight union - prevents passage of water and solutes between the two cells 3. Attachment: also form extensive connections between each other

2. Desmosomes: comprised of a. plaque of proteins inside the plasma membrane -the plaque attaches to the intermediate filaments of the cytoskeleton (keratin) b. cellular adhesion proteins/CAMs called cadherins

Epithelial characteristics Epithelial characteristics 3. Gap junctions: two cells held together by proteins called connexons -connexons are channel proteins -materials can freely move between the two cells -passage of materials helps to coordinate the activities of the adjacent cells e. g beating rhythm of cilia

Epithelial characteristics 4. Avascularity: do not contain blood vessels -must obtain nutrients via diffusion or absorption 5. Regeneration: damaged cells are replaced through differentiation of stem cells located deep within the tissue -rate of renewal depends on rate of cell death -stem cells = germinative cells -these cells are found closest to the basement membrane -migrate towards the surface and differentiate into epithelial cells

Classification of Epithelia catagorizing epithelial tissue types A. # of layers simple = 1 layer stratified = multiple **pseudo = 1 layer B. Cell shape columnar cuboidal squamous

Classification of Epithelia

Simple Squamous Epithelium -tile-like cells - cells are thin, flat and irregular in shape = squamous -simple squamous - most delicate tissue in the body -found in protected regions where absorption occurs -many types: e.g. mesothelium - lines the abdomen e.g. endothelium - lines heart chambers and vessels

Stratified Squamous Epithelium -stratified squamous - where mechanical stresses are severe -cells on exposed surfaces may contain keratin – a protein that reduces water loss and provides strength = keratinized epithelium -non-keratinized epithelium is tough but must be kept moist = e.g. oral mucosa

-four types of cells: Stratified Squamous Epithelium – the Epidermis 1. keratinocytes – make up the majority of the epidermis -epithelial cells that synthesize the protein keratin 2. melanocytes – cells for the synthesis of the light absorbing pigment melanin 3. Merkel cells – neurons that detect pressure 4. Langerhans cells – immune responses

5 layers maximum Stratified Squamous Epithelium – the Epidermis Stratum Basale/Germinativum Stratum Spinosum Stratum Granulosum Stratum Lucidum Stratum Corneum

Epidermis: layers -stratum basal/germinativum: -inner most/deepest layer of the epidermis - attached firmly to the basement membrane between epidermis & dermis underneath - contain germinative stem cells that differentiate into the keratinocytes and melanocytes of the epidermis -Merkel cells are found in hairless regions- pressure and touch receptors - stratum spinosum: several layers of keratinocytes -keratinocytes of the stratum basale migrate into this layer -keratinocytes are interconnected by desmosome for strength -keratinocytes can divide to increase thickness of this layer -melanocytes are common -Langerhans cells of the immune system also found in the more superficial layers

Epidermis: layers -stratum granulosum: -made up of keratinocytes migrating up from the stratum spinosum -cells synthesize large quantities of proteins (including keratin) – cytoplasm appears granular -as more and more keratin is made – keratinocytes become thinner and flatter -the cells then die and dehydrate

Epidermis: layers -stratum lucidum: -flattened, densely packed cells filled with keratin -have a glassy appearance because they do not stain well -present only in the skin of fingertips, palms & soles B. stratum lucidum C. stratum spinosum D. stratum granulosum A. stratum corneum

Epidermis: layers - stratum corneum: cornu = horn -15-30 layers of flattened, dead, interlocking cells -if large amounts of keratin are present – the tissue is said to be “cornified” - keratin makes this layer water-resistant - very dry to prevent growth of bacteria -kept moist by oily secretions from sebaceous glands -penetration is promoted by attachment to a lipid or dissolution in a lipid-based solutions -transdermal drug patches – drugs are in oils or lipid-soluble carriers - moisturizing lotions – only penetrate few first layers of corneum -takes 15-30 days to move from germinativum to corneum -cells will remain in corneum for an additional 2 weeks before being shed

Transitional Epithelium -stratified squamous epithelium that permits stretching -located in walls of the bladder, renal pelvis and the ureters e.g. bladder wall - when empty the epi. looks as if it has several layers -actual number of layers can be seen upon stretching

Transitional Epithelium

Simple Cuboidal Epithelium -cells are cubes -big, round nucleus found in the center of the cell -found in regions of secretion and absorption e.g. kidney tubules pancreas & salivary glands - buffers & enzymes thyroid follicles - thyroid hormones

Simple Cuboidal Epithelium

Simple Columnar Epithelium -height is greater than their width -oval shaped nuclei found close to the BM & aligned with each other -simple columnar: found in areas of absorption and secretion -located in the gallbladder, larger ducts of exocrine glands, gastric pits of stomach -frequently the apical face is modified with microvilli e.g. intestinal lining = brush border -short-lived cells – replaced every 4 to 5 days -frequently found with Goblet cells (intestine and stomach)

Simple Columnar Epithelium microvilli wandering lymphocytes

Pseudostratified Columnar Epithelium -pseudostratified columnar: only a single layer despite looking like many -nuclei are at varying levels - appearance of multiple layers -BUT basal face of every cell contacts the BM -exposed apical surface typically bears cilia e.g. respiratory epithelium

Pseudostratified Columnar Epithelium -these tissues are generally ciliated

Type: Simple squamous Simple cuboidal Simple columnar Pseudostratified columnar Stratified squamous Description: single layer, flattened cells single layer, cube-shaped cells single layer, elongated multiple layers, flattened Function: filtration, diffusion, osmosis secretion, absorption protection, secretion, absorption protection, secretion, movement of mucus protection Location: lungs, linings of blood vessels ovaries, kidneys, certain glands linings of uterus, stomach and intestines linings of respiratory passages and reproductive outer layer of skin, oral cavity, throat

Glandular Epithelium epithelial cells specialized to produce and secrete substances gland = single epithelial cell OR multiple cells two types of glands: 1) exocrine = secrete into ducts e.g. sweat glands 2) endocrine = secrete directly into bloodstream e.g. thyroid, pituitary ** one gland is mixed - e.g. pancreas

exocrine gland structure: Unicellular: single-celled glands e.g. goblet cells SIMPLE COLUMNAR with GOBLET CELLS -goblet cells = unicellular exocrine glands that secrete mucus

exocrine gland structure: Multicellular glands – multiple cells grouped together multicellular glands can be classified based on: 1. Mode of secretion – used by physiologists Merocrine Apocrine Holocrine 2. Consistency of secretion – used by histologists Serous Mucus Mixed 3. Structure – used by histologists shape of the secretory portion branching pattern of the duct simplest multi-cellular gland is a secretory sheet e.g. gastric epithelium

Serous Glands 1. serous - watery fluid that contains enzymes e.g. saliva – parotid salivary gland

Mucus Glands 2. mucous - glycoproteins called mucins that absorb water to form a slippery mucus

Mixed Glands 3. mixed - more than one type of gland cell -produces different types of secretions - mucus and serous e.g. submandibular or sublingual salivary gland

Connective Tissue binds structures together provides support produces blood fills cavities protects organs

Connective Tissue components: matrix + cells -matrix: non-cellular support material -comprised of extracellular protein fibers – mainly collagens e.g. 1. collagen fibers (white) – collagen type I 2. elastic fibers (yellow) 3. reticular fibers – collagen type III 4. fibronectin -plus a ground substance = water + hyaluronan (sugar), proteoglycans and glycoproteins -cells: secrete the matrix -some have become very specialized and make a very specialized matrix

The way I organize Connective tissues Loose – areolar CT, adipose & reticular Dense – dense (regular, irregular), elastic Supportive – bone & cartilage Fluid – blood

Types: 1. Areolar 2. Dense – regular and irregular 3. Adipose Cartilage Bone Blood Description: Cells in fluid-gel matrix Cells in solid-gel matrix Cells in solid matrix Cells in fluid matrix Function: Binds organs together, holds tissues, fluids Protects, insulates and stores Binds organs together Supports, protects, provides framework provides framework Transports gases, defends against disease, clotting Types: 1. Areolar 2. Dense – regular and irregular 3. Adipose 4. Cartilage 5. Bone 6. Blood

Loose connective tissues: Loose Areolar tissue -cells are mainly fibroblasts, spaced far apart -matrix: mostly ground substance + collagen fibers, elastic fibers -cushions and can be distorted due to loose organization e.g. found beneath the dermis connecting it to muscle and bone

Loose connective tissues: Adipose tissue -cells = adipocytes (fat storing fibroblasts) -cushions joints and organs -stores energy -insulates -often found intermixed with areolar tissue

Dense connective tissues: types -most of the tissue is densely packed extracellular matrix fibers of collagen type I -cells are fibroblasts -often called fibrous tissue -two types: 1) dense regular – dense & elastic in nature e.g. tendons, ligaments 2) dense irregular - interwoven meshwork or fibers -e.g. dermis of skin, perichondrium of joints and periosteum of bone

Dense connective tissues: Dense Regular Connective -few fibroblasts - multiple, closely packed collagen I fibers - fine network of elastic fibers e.g. tendons, ligaments

Dense connective tissues: Dense Irregular Connective found in the deepest layers of the dermis = also called the reticular layer (don’t confuse it with reticular tissue)

Connective Tissue: The Dermis -two major components: 1. papillary layer 2. reticular layer Papillary Layer -about 1/5th thickness of dermis -loose areolar connective tissue -well vascularized and innervated -dermal projections into the epidermis = dermal papillae -some papillae contain Meissner’s corpuscles for touch -also free nerve endings – project into the epidermis - sensations of pain, warmth, itching Reticular Layer (“little net”) -dense irregular connective – interwoven collagen bundles plus elastic fibers -contains blood vessels, nerves, hair follicles, sweat glands and sebaceous/oil glands -also contains lamellated corpuscles (Pacinian corpuscles) that detect deep touch and pressure

Supportive Connective tissues: Bone & Cartilage -cartilage & bone -see your lecture on the skeletal system

Fluid Connective tissue: Blood -cells suspended in a fluid matrix = plasma -plasma ~ 55% blood volume -inorganic salts -organic substances - e.g. sugars, proteins -cells: 1) RBCs - biconcave, disc-shaped -contains hemoglobin - 4 globin proteins + heme group (iron) 2) WBCs - fight infection = leukocytes - many types: a. monocytes/macrophages b. lymphocytes - T and B cells c. basophils - histamine d. neutrophils - 1st at infection e. eosinophils - allergic response 3) platelets - blood clotting response

Membranes -superficial epithelial sheet + underlying connective layer (called a lamina propria) -cover & protect -four types: 1. serous 2. mucous 3. cutaneous 4. synovial

1. Serous membranes -line the subdivisions of the abdominopelvic cavity and thoracic cavity -covers, protects and moistens/lubricates -comprised of an epithelial layer (simple squamous epithelium) called a mesothelium + underlying loose areolar connective tissue -the mesothelium secretes a watery fluid = serous fluid (separates and lubricates the movement of organs) -divided into two separate layers: 1)outer parietal layer - lines the cavity 2) inner visceral layer - covers organs -serous membrane lining the pleural cavity (lungs) = pleura - serous membrane lining the pericardial cavity (heart) = pericardium - serous membrane lining the peritoneal cavity (abdomen) = peritoneum

2. Mucous membranes -line cavities that directly communicate with the exterior environment e.g. respiratory, urinary, reproductive, digestive -covers, protects and moistens/lubricates -epithelial layer (simple squamous, simple cuboidal, simple columnar) is kept moist through production of mucus by glands, other glandular secretions or exposure to fluids (e.g. urine) -in areas of physical stress = stratified epithelial tissue rather than simple -connective tissue layer is loose areolar tissue = lamina propria --supports embedded blood vessels and nerves

3. Synovial membranes -lines & lubricates the synovial joint cavity - to permit easy movement of bones over each other -bones are covered by incomplete layers of simple squamous or cuboidal epithelial cells -some cells within the synovial membrane are phagocytic to remove pathogens -others are secretory - secrete a watery synovial fluid for lubrication

4. Cutaneous membrane (skin) -covers the surface of the body -22 sq. ft or 16% of body weight -epithelial layer is keratinized stratified squamous = epidermis -underlying tissue is areolar tissue reinforced with dense connective tissue = dermis -skin is attached to underlying muscle and bone by areolar tissue + adipose -skin turns in at the mouth, nasal cavity, anus and urethral and vaginal openings – meets the mucous membranes lining these cavities 1. physical protection: protection from microbes, abrasion, heat 2. chemical protection – keratin - dryness of the epidermis; salt of sweat 3. regulation of water exchange: by sweating 4. regulation of body temperature: thermoregulation -by sweating & adjusting blood flow through the dermis 5. excretion of wastes -by sweating 6. nutrition – synthesis of vitamin D precursor -activated in skin, converted to calcitrol in liver 7. sensation: touch, pressure, vibration, pain & thermal 8. immune defense: Langerhans cells of the epidermis

Muscular Tissue specialized for contraction very distinct organelles within the cells 3 types 1. skeletal – voluntary muscle 2. cardiac – involuntary muscle 3. smooth – involuntary muscle

Skeletal Muscle: voluntary muscle -voluntary nervous control -repeating banding patterns of actin & myosin = striated appearance -mature cells = multi-nucleated cells – made from fusion of myoblasts -cells are very long – sometimes called muscle fibers -cannot divide – but new cells form from differentiation of myogenic stem cells = satellite cells -attached to bones via tendons

Cardiac Muscle: involuntary muscle -cells are striated but uni-nuclear = cardiomyocytes -incapable of dividing – PLUS there are no satellite cells -therefore damaged heart muscle cannot be regenerated -identified by the presence of intercalated discs -for cell-cell communication and force transmission

Smooth Muscle: involuntary muscle -lines blood vessels, airways and organs -non-striated -spindle shaped cells - single nucleus (uni-nuclear) -control their own rate of contraction through action of pacemaker cells -BUT nervous system can also control contraction -slow, sustained & strong contraction

Neural Tissue (Nervous Tissue) specialized for the conduction of electrical impulses from one body region to another two types of neural cells: 1) neurons 2) glial cells – astrocytes, oligodendrocytes, microglia