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Tissues
-four primary tissue types:
1. Epithelial
2. Connective
3. Muscle
4. Neural
Epithelial Tissue
= lining epithelium & glands
•multiple functions of epithelial tissues:1.protection - from dehydration, pathogens2.synthesis – e.g. vitamin D3. regulation - e.g. body temperature4. excretion - e.g. waste5. immune response6. control of permeability – every substance must cross an epithelial membrane first7. sensitivity – epithelial membranes are well-innervated
• lining epithelium = line body surfaces and cavities• glandular epithelium = secretion
Epithelial characteristics
1.Cellularity2.Polarity3.Attachment
1. to each other2. to connective tissue
4.Avascularity5.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 exteriorof the body - apical face-also has an attached base which is anchored to other tissues - basal face-the organelles are not uniformly distributed
3. Attachment: attached to underlying tissues via the basement membrane
Epithelial characteristics
-BM is produced by the basal surface of the cells & connective tissue
-the BM is comprised of two layersa. closest to epithelial cell = basal lamina(glycoproteins, laminin and actin)
-acts as a barrier to transport
b. furthest from the epithelialcell = reticular lamina
-collagen IV bundles producedby the underlying connectivetissue 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
Epithelial characteristics
2. Desmosomes: comprised ofa. 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
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
Epithelial characteristics
Classification of Epithelia
A. # of layerssimple = 1 layerstratified = multiple**pseudo = 1 layer
B. Cell shapecolumnarcuboidal squamous
• catagorizing epithelial tissue types
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 - 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
Stratified Squamous Epithelium
Stratified Squamous Epithelium – the Epidermis
-four types of cells:1. keratinocytes – make up the majority of the epidermis
-epithelial cells that synthesize the protein keratin2. melanocytes – cells for the synthesis of the light absorbing pigment melanin3. Merkel cells – neurons that detect pressure4. Langerhans cells – immune responses
Stratified Squamous Epithelium – the Epidermis
5 layers maximum1. Stratum Basale/Germinativum2. Stratum Spinosum3. Stratum Granulosum4. Stratum Lucidum5. Stratum Corneum
-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
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
- 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
Epidermis: layers
-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
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)
wandering lymphocytesmicrovilli
Simple 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
Pseudostratified Columnar Epithelium
Type:
Simple squamous
Simple cuboidal
Simple columnar
Pseudostratifiedcolumnar
Stratified squamous
Description:
single layer, flattened cells
single layer, cube-shapedcells
single layer, elongatedcells
single layer, elongatedcells
multiple layers, flattened cells
Function:
filtration, diffusion, osmosis
secretion, absorption
protection, secretion, absorption
protection, secretion, movement of mucus
protection
Location:
lungs, linings of bloodvessels
ovaries, kidneys, certainglands
linings of uterus, stomachand intestines
linings of respiratorypassages and reproductive
outer layer of skin, oralcavity, throat
• epithelial cells specialized to produce and secrete substances
Glandular Epithelium
•gland = single epithelial cell OR multiple cells
•two types of glands: 1) exocrine = secrete into ductse.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
2. mucous - glycoproteins called mucins that absorb water to form aslippery mucus
Mucus Glands
3. mixed - more than one type of gland cell-produces different types of secretions - mucus and serouse.g. submandibular or sublingual salivary gland
Mixed Glands
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 collagense.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 veryspecialized matrix
The way I organize Connective tissues
• Loose – areolar CT, adipose & reticular
• Dense – dense (regular, irregular), elastic
• Supportive – bone & cartilage• Fluid – blood
Types:1. Areolar2. Dense – regular and irregular3. Adipose4. Cartilage5. Bone6. Blood
Type:
Areolar
Adipose
Dense
Cartilage
Bone
Blood
Description:
Cells in fluid-gel matrix
Cells in fluid-gel matrix
Cells in fluid-gel matrix
Cells in solid-gel matrix
Cells in solid matrix
Cells in fluid matrix
Function:
Binds organs together,holds tissues, fluidsProtects, insulates andstoresBinds organs together
Supports, protects, provides frameworkSupports, protects, provides frameworkTransports gases, defendsagainst disease, clotting
-cells are mainly fibroblasts, spaced far apart-matrix: mostly ground substance + collagen fibers, elastic
fibers-cushions and can be distorted due to loose organizatione.g. found beneath the dermis connecting it to muscle and
bone
Loose connective tissues: Loose Areolar tissue
-cells = adipocytes (fat storing fibroblasts)
-cushions joints and organs-stores energy-insulates-often found intermixed with areolar
tissue
Loose connective tissues: Adipose 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
-few fibroblasts- multiple, closely packed collagen I fibers- fine network of elastic fibers
e.g. tendons, ligaments
Dense connective tissues: Dense Regular Connective
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 theepidermis - sensations of pain, warmth, itching
Reticular Layer (“little net”)-dense irregular connective – interwovencollagen bundles plus elastic fibers-contains blood vessels, nerves,hair follicles, sweat glands andsebaceous/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
-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 cellsc. basophils - histamined. neutrophils - 1st at infectione. eosinophils - allergic response
3) platelets - blood clotting response
Fluid Connective tissue: Blood
Membranes
-four types:
1. serous
2. mucous
3. cutaneous
4. synovial
-superficial epithelial sheet + underlying connective layer(called a lamina propria)
-cover & protect
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
-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
-covers, protects and moistens/lubricates
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 & thermal8. 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
-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
Skeletal Muscle: voluntary 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
Cardiac 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
Smooth Muscle: involuntary muscle
Neural Tissue (Nervous Tissue)
•specialized for the conduction of electrical impulses from one bodyregion to another
1) neurons
2) glial cells – astrocytes, oligodendrocytes, microglia
•two types of neural cells:
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