ch4 tissues

Tissues

group of cells with a common embryonic origin

that function together to carry out specialized activity

Tissues include various types

• ranging from hard (bone) to semisolid (fat) to liquid (blood)

Epithelial tissues

cover body surfaces, line hollow organs, body cavities, and ducts. They also form glands

Connective tissues (CT)

• protect, support, and bind organs

• Fat is a type of CT that stores energy

• Blood is a fluid type of CT

• Muscular tissues

generate the physical force needed to make body structures move. They also generate heat used by the body

Nervous tissues

• detect changes in the body and respond by generating nerve impulses

Cell Junctions

Tissues are formed by grouping cells together using a variety of cell junctions

• The 5 most important kinds of cell junctions are

• Tight junctions

• Adherens junctions

• Desmosomes

• Hemidesmosomes

• Gap junctions

Tight junctions

are found where a leakproof seal is needed between cells

• Keep materials from leaking out of organs like stomach and bladder.

Adhererns junctions

• contain plaque-- a dense protein layer inside the plasma membrane

• Help epithelial surfaces resist separation during various contractile activities. Ex. Food moving through intestine

Desmosomes

act as "spot welds"

• Common among epidermal cells and cardiac muscle cells

• Hemidesmosomes

(look like half of a desmosome) are "half-welds" that join cells to the basement membrane

Gap junctions

are pores (connexons) that allow small substances like ions to pass between cells.

• Seen between cardiac muscle cells and between some smooth muscle cells-allow electrical signals to pass very rapidly between the cells

Comparison: Epithelial vs.

Connective Tissue

Cell to extra cellular matrix ratio: EPITHELIAL

many tightly packed cells with little or no extracellular matrix.

Comparison: Epithelial vs.

Connective Tissue

Cell to extra cellular matrix ratio: CONNECTIVE

• fewer cells with more matrix.

Comparison: Epithelial vs.

Connective Tissue

Blood vessels: epithelial

• has no blood vessels.

Comparison: Epithelial vs.

Connective Tissue

Blood vessels: Connective tissues

have significant networks of blood vessels.

(Epithelial/Connective) tissues almost always form surface layers and are not covered by another tissue

epithelial

Epithelial tissue (aka "epithelium") is used to

cover and line structures and to make glands

• Glands secrete things like mucous, hormones, and other substances

All epithelia have a ___ ___ surface and an attached __ surface

• free apical

• basal

Basal layer of epithelium secretes ____ ____, underlying connective tissue secretes reticular lamina.

• Together these laminae form a non-cellular basement membrane on which the epithelium sits.

basal lamina

Basal layer of epithelium secretes basal lamina, underlying connective tissue secretes ____ ____.

• Together these laminae form a non-cellular basement membrane on which the epithelium sits.

• reticular lamina.

Basal layer of epithelium secretes basal lamina, underlying connective tissue secretes reticular lamina.

• Together these laminae form a non-cellular ____ ____ on which the epithelium sits.

• basement membrane

One layer. All cells touch B.M.

Really just one layer, all cells touch B. M.

Two or more layers. Only basal layer touches B. M.

Flat, wide "paving stone" cells

Cuboidal

Cells as tall as they are wide

Cells taller than they are wide

• There are 8 types of epithelium:

• Simple squamous

• Stratified squamous

• Simple cuboidal

• Stratified cuboidal

• Simple columnar

• Stratified columnar

• Pseudostratified columnar • Transitional

With stratified types, if different shapes are present in layers, the epithelium is always named by the…

shape of cells in the apical (outermost) layer

Simple squamous epithelium

single layer of flat cells

• Found in air sacs of lungs, linings of blood vessels
  (endothelium) / heart (endocardium) / lymphatic vessels, capillaries, and as epithelial part of serous membranes (mesothelium).

• Simple Cuboidal Epithelium =

• single layer of cube-shaped cells

• Found lining tubules of the kidneys.

Simple columnar epithelium

single layer of column-shaped cells. 2 forms: nonciliated (ex. lines GI tract, note cells do have microvilli) and ciliated (ex. lines bronchioles).

• Has goblet cells (mucous-secreting cells)

• Pseudostratified columnar epithelium

• nuclei at different depths makes it look stratified (all cells attached to basement membrane, but not all reach apical surface). 2 forms:

nonciliated (ex. epididymis) and ciliated (ex. upper airways).

• Only ciliated has goblet cells

Stratified Squamous Epithelium

has apical surface made up of flat cells

• Other layers have different shapes, but name is based on apical layer

• Many layers are ideal for protection against strong friction forces

Keratinized form

• a tough layer of keratin (a protein resistant to friction and repels bacteria) present on surface. (ex. epidermis, aka skin)

Nonkeratinized form

• does not contain keratin and remains moist. (ex. vagina)

Stratified Cuboidal Epithelium

apical surface made of two or more layers of cube-shaped cells

• Rare (ex. sweat glands, part of male urethra)

Stratified Columnar Epithelium

apical surface made of columnar cells

• Uncommon (ex. parts of urethra)

Transitional Epithelium

cells change shape depending on the state of stretch in the tissue

• Apical "dome cells" (seen here in relaxation) are an identifiable feature and signify an empty bladder.

• In full bladder, the cells are flattened.

Glandular Epithelium

endocrine glands

Glands that secrete their contents directly into the blood ("ductless glands"). Ex. pituitary gland, thyroid gland, and adrenal gland.

exocrine glands.

Glands that secrete their contents into a duct are calleds. Ex. sweat glands, gastric glands, salivary glands

glandular epithelium

Types of secretions of exocrine glands

mucus, sweat, oil, earwax, saliva, and digestive enzymes

Glandular Epithelium

• Some exocrine glands are

unicellular (ex. goblet cells), but most are multicellular.

Structurally, multicellular glands are classified by 2 criteria: (1/2)

• Duct portion - is it branched or unbranched?

• Simple= no branching

• Compound = branching

Structurally, multicellular glands are classified by 2 criteria: (2/2)

• Secretory portion

what is the shape?

• Tubular

• Acinar (berry-shaped, aka alveolar)

• Tubuloacinar - combo of both

merocrine

most common type, secretion by exocytosis. Ex. salivary glands.

Apocrine

• fluid builds up at apical end of cell and then the end just busts off--cell repairs itself later. Ex. mammary glands

• Holocrine

• whole cell just ruptures (and dies) releasing contents. Ex. sebaceous (oil) glands.

Connective Tissue functions

Numerous functions:

• Bind tissues together

• Support and strengthen tissue

• Protect and insulate internal organs

• Compartmentalize and transport

• Energy reserves and immune responses

• All CT tend to have ___ cells separated by ________

• sparse

• lots of extracellular matrix

collagen

main protein of CT and most abundant protein in the body--about 25% of total protein content

Connective Tissue Cells

• Fibroblasts

• usually most abundant cell type, secrete fibers and matrix.

Connective Tissue Cells

• Macrophages

• develop from monocytes (a type of white blood cell), they're phagocytic.

• Connective Tissue Cells

• Plasma cells

• develop from antibody-producing B
  lymphocytes (aka B cells)

Connective Tissue Cells

• Mast cells

abundant alongside blood vessels, produce histamine

Connective Tissue Cells

• Adipocytes(aka fat cells)

store energy in the form of fat

Connective Tissue Extracellular Matrix

a Consists of 2 major parts:

• Ground substance

• - supports, binds, and provides medium for exchange between blood and cells (hyaluronic acid, chondroitin sulfate, etc.)

Connective Tissue Extracellular Matrix

a Consists of 2 major parts:

Fibers- CT cells make 3 common fibers:

• Collagen fibers

• - very tough, stretch resistant, particularly important in bone, cartilage, tendons, and ligaments,

Connective Tissue Extracellular Matrix

a Consists of 2 major parts:

Fibers- CT cells make 3 common fibers:

• Elastic fibers -

• made of elastin, strong and stretchy, found in skin, blood vessels, and lungs

Connective Tissue Extracellular Matrix

a Consists of 2 major parts:

Fibers- CT cells make 3 common fibers:

Reticular fibers

— made of collagen and glycoprotein, strong supporting network
around fat cells, nerve fibers, and muscle fibers

Connective Tissue Classification

• Embryonic connective tissue

• Mesenchyme

• Mucous connective tissue

Connective Tissue Classification

mature connective tissue

• Loose connective tissue - subtypes: areolar, adipose, reticular

• Dense connective tissue - subtypes: dense regular, dense irregular, elastic

• Cartilage - subtypes: hyaline, fibrocartilage, elastic

• Bone

• Liquid connective tissue - subtypes: blood, lymph

Embryonic Connective Tissues

2 Embryonic Connective Tissues:

• Mesenchyme

• gives rise to all other connective tissues

Embryonic Connective Tissues

2 Embryonic Connective Tissues:

• Mucous CT (aka Wharton's Jelly) -

gelatinous substance in the umbilical cord of fetus

Mature Connective Tissues

Loose Connective Tissues subtype

• Areolar connective tissue

• is most widely distributed CT in body. It. contains several types of cells and all three fiber types.

• Used to attach skin and underlying
  tissues, and as a packing between glands, muscles, and nerves

Mature Connective Tissues

Loose Connective Tissues subtype

• Adipose tissue (aka fat tissue)

is located in subcutaneous layer deep to skin and around organs and joints

• Reduces heat loss and serves as padding and energy source

Mature Connective Tissues

Loose Connective Tissues subtype

• Reticular connective tissue

is network of reticular fibers and cells

• Forms a scaffolding used by cells of lymphoid tissues, such as spleen and lymph nodes

Mature Connective Tissues

Dense Connective Tissues

• Dense Regular Connective Tissue

• consists of collagen fibers and comprise tendons and ligaments where the need for strength along one axis is mandatory (a muscle pulling on a bone).

Mature Connective Tissues

Dense Connective Tissues

• Dense Irregular Connective Tissue

• consists mostly of fibroblasts and collagen fibers randomly arranged

• Provides strength when forces are pulling from many different directions

Mature Connective Tissues

Dense Connective Tissues

• Elastic Connective Tissue

• consists mostly of fibroblasts and freely branching elastic fibers

• Allows stretching of certain tissues like the elastic arteries (ex. the aorta)

Cartilage

has a rubbery consistency. It has a poor blood supply and grows slowly.

When injured, repair is slow

• Hyaline cartilage

• is most common type, it covers ends of long bones and parts of ribs, nose, trachea, bronchi, and larynx.

• Provides a smooth surface for joint movement

• Fibrocartilage

has thick bundles of collagen fibers and is very strong

• Fibrocartilage discs in the intervertebral spaces and the knee joints support the huge loads up and down the long axis of the body.

• Elastic cartilage

consists of chondrocytes located in a threadlike network of elastic fibers, very flexible

• Makes up the malleable part of the external ear and the epiglottis

Bone

has a calcified extracellular matrix that makes it very hard. Bone tissue is often derived from cartilage

Liquid connective tissues

- blood and lymph. Blood consists of cells (RBCs, WBCs, and platelets) in a liquid extracellular matrix called plasma

Membranes

• are flat sheets of pliable tissue that cover or line a part of the body

• Epithelial membranes

• = epithelium + connective tissue

• Mucous membranes (or mucosa)

• Mucous membranes line "interior" body surfaces open to the outside: digestive tract, respiratory tract, reproductive tract.

• Its connective tissue is called lamina propria.

• Serous membranes (or serosa)

• Serous membranes line some internal surfaces. Ex: pleura, pericardium, and peritoneum

• Cutaneous membrane

skin

• Synovial membranes

• = connective tissue only; help form capsule around movable joints, such as elbow, hip, and knee

muscle tissue

consists of fibers that provide motion, maintain posture, and produce heat

3 types of muscle tissue

• Skeletal muscle

• Cardiac muscle

• Smooth muscle

Nervous Tissue

• Two kinds of cells:

• Neurons

• Neuroglia

• Most neurons have

• a cell body, dendrites, and an axon

• They carry sensory and motor information and perform integrative functions

• Neuroglia

• protect and support neurons

Neurons and muscle fibers are considered

excitable cells because they have electrical excitability, the ability to respond to certain stimuli by producing electrical signals such as action potentials

• Action potentials can travel along the plasma membrane of a neuron or muscle fiber

tissue repair

• Epithelial tissue capacity to renew cells

• excellent at cell renewal

tissue repair

• CT capacity to renew cells

• okay at cell renewal; depends on specific type

Tissue Repair

• Muscle tissue capacity to renew cells

• is poor at cell renewal

Tissue Repair

• nervous tissue capacity to renew cells

is the worst at cell renewal.

Repair by tissue types

• Epithelial cells are replaced by the division of

undifferentiated stem cells or by mature, differentiated cells

Fibrosis

• is the process of scar formation: fibroblasts make collagen fibers and other materials to fill in the damaged area (scar tissue). Function is often lost.

• Granulation tissue

• actively growing connective tissue that serves as a framework for epithelial cell migration during wound healing

• Autoimmune disorders

are the most common CT disorders

• Sjogren's syndrome

• -many exocrine glands destroyed (lacrimal, salivary) - widespread dryness, fatigue, arthritis

• Systemic lupus erythematosus

• chronic inflammatory disease, painful joints, fever, fatigue range from mild to fatal

Pseudostratified

Really just one layer, all cells touch B. M.