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: