General

1. Specialization - multicellulars, cells specialized, perform unique functions

2. Tissues - groups of cells; similar structure; perform same or related functions

3. Histology - the study of tissues

4. Tissue types - four main groups of tissues; simplistic scheme functions

-a. Epithelial - coverings

-b. Connective - support

-c. Muscle - movement

-d. Nervous – control

Cell junctions and other membrane specialization

1. Microvilli - minute finger-like extensions membrane greatly increase surface area

2. Membrane junctions - hold cells; tight junctions, desmosomes, and gap junctions

3. Tight junctions - protein molecules fuse together like zipper; stop leakage

-a. Digestive tract – epithelial cells; prevents leakage of enzymes, microorganism

4. Desmosomes - mechanical couplings or scattered like rivets along adjacent cells

-a. Intermediate filaments – part of the cytoskeleton of cell; connect to plaque

-b. Plaque – thickening on cytoplasmic side of membrane

-c. Linker proteins – from plaque; interdiginate with linkers proteins, adjacent cells

-d. Mechanical tissue - like muscle and skin; stops from pulling apart

5. Gap junctions - Allows passage of chemical substances between adjacent cells

-a.Connexons - cylinders going from one cell to the next; transmembrane

-b. Excitable tissue - heart; passage of ions for coordination of electrical stimulation

EPITHELIAL TISSUE

General comments

1. Covering – or linings; boundaries between body and environment

2. Glandular epithelium - makes up glands of the body

3. Functions - protection, absorption, filtration, excretion, secretion, and sensory

Special characteristics

1. Cellularity - almost entirely of cells little extracellular material between them

2. Cell junctions – many; continuous sheet

-a. Tight junctions – zipper like, prevents leakage

-b. Desmosomes – rivet like, prevents tearing

3. Polarity - epithelial tissue has two distinct surfaces

-a. Apical surface - free surface; exposed

-b. Basal surface - attached surface to connective tissue

4. Innervated - is supplied by nerve fibers

5. Avascular - no blood vessels; nutrients from underlying connective tissue

6. Regeneration – exposed; constantly being replaced via mitosis

Basement membrane

1. Basal lamina - adhesive glycoprotein sheet from epithelial cells; selective; repair

2. Connective tissue support - all epithelium is supported by connective tissue

3. Reticulum lamina - deep to basal lamina; collagen fibers from connective tissue

4. Basement membrane - basal lamina and the reticulum lamina

5. Lamina propria – connective tissue in mucus membrane; areolar tissue

Epithelial classification

1. Cell layers – either one, or more than one

-a. Simple epithelium - epithelial tissue which has only one cell layer

-b. Stratified epithelium - 2 or more layers; naming based on cell on apical surface

2. Cell shape - length which is reflected by shape of nucleus

-a. Squamous epithelium - flat scale like cells; nucleus disc like

-b. Cuboidal epithelium - height and width equal; nucleus round and central

-c. Columnar epithelium - taller than they are wide; nucleus elongated; basal end

Types of Epithelial Tissue

Simple squamous epithelium

1. Description - single layer of flattened cells; flattened nucleus

2. Location - air sacs of lungs; glomeruli of kidneys

3. Function - diffusion (alveoli) and filtration (kidney glomeruli)

Simple cuboidal epithelium

1. Description - single layer of cuboidal cells; large round central nucleus

2. Location - kidney tubules; small glands; ovary surface

3. Function - secretion and absorption

Simple columnar epithelium

1. Description - single layer of columnar epithelium with oval basally located nuclei

-a. Cilia - in respiratory system; reproductive surface

-b. Goblet cell - mucus producing cells

-c. Microvilli - in digestive system

2. Location - gastrointestinal tract from stomach to anus; small bronchi

3. Function - absorption; secretion of mucus, enzymes, and; ciliated propel

Pseudostratified columnar epithelium

1. Description - single layer; varying height which gives it a stratified appearance

-a. Cilia - trachea and most of upper respiratory system

-b. Goblet cells - as in columnar; produce mucus

2. Location – depends on type

-a. Cilated - trachea and upper respiratory system;

-b. Nonciliated - in ducts of large glands and male urethra

3. Function - secretion of mucus and propulsion by cilia

Stratified squamous epithelium

1. Description - apical layer squamous; basal layer cuboidal (sometimes columnar))

2. Location - depends on type

-a. Keratinized - epidermis of the skin; apical cells are dead

-b. Nonkeratinized - lining of mouth, esophagus, anus, and vagina

3. Function - protects underlying tissue from abrasion

Stratified columnar epithelium

1. Description - several layers; apical layer columnar; basal layer usually cuboidal

2. Location - rare; some parts male urethra; large ducts of some glands

3. Function - protection and secretion

Transitional epithelium

1. Description – apical, cuboidal to squamous, stretched; basal cuboidal, columnar

2. Location - ureter, bladder, and part of urethra

3. Function - stretches allowing urinary organs to retain urine

Glandular Epithelia

General comments

1. Gland - a structure of one or more cells; makes and secretes a particular product

2. Golgi apparatus - produce numerous secretory granules

3. Endocrine glands –ductless; hormones released into extracellular fluid

4. Exocrine glands – release products to apical surfaces

Multicellular exocrine glands

1. Basic structure

-a. Secretory unit - epithelial tissue, produces secretion

-b. Duct - epithelial tissue; passage secretion to body surface

-c. Supporting connective tissue - provides nutrients blood vessels and nerves

-d. Fibrous capsule – may form from connective tissue; divides gland into lobes

2. Structural classification – branching of duct; shape of secretory unit

-a. Simple - unbranched duct

-b. Simple branched – unbranced duct; secretory units branch off it

-c. Compound - branched duct

-d. Tubular - if secretory unit forms tube

-e. Alveolar (acinar) - if secretory forms flask like sacs

-f. Tubuloalveolar - if there is a mixture

3. Functional classification – how secretion is released

-a. Merocrine gland - release secretion by exocytosis (most)

-b. Holocrine gland - cell rupture; high rate of mitosis; sebaceous gland

-c. Apocrine gland - apex of cell pinches off; mammary maybe; merocrine by most

Unicellular exocrine glands

1. Goblet cells - single cells; epithelia respiratory, digestive system; only one humans

2. Golgi apparatuses - numerous

3. Mucin - glycoprotein produced by these cells

4. Mucus – slimy; mucin mixes with water; protects and lubricates surfaces

CONNECTIVE TISSUE

General

1. Distribution - most abundant and widely distributed tissue type in body

2. Functions - binding and support, protection, insulation, and transportation

Common characteristics

1. Common origin - all arise from the same embryonic tissue (mesenchyme)

2. Vascularity - vary from highly vascularized to avascular

3. Extracellular matrix - most much; external to cell (fibers and ground substance)

Structural elements

1. Ground substance - amorphous substance; fibers and cells are imbedded

–a. Proteoglycans – protein core; polysaccharides side chains (glycosaminoglycans)

2. Fibers - provide support to connective tissue

-a. Collagen fibers - most abundant, thickest, providing tensile strength, white fibers

-b. Elastic fibers - made of elastin, stretch and recoil, yellow fibers

-c. Reticular fibers – collagen; basement membrane

3. Fundamental cell types – immature (-blast); mature (-cyte)

-a. Fibroblast / fibrocyte - found in connective tissue proper

-b. Chondroblast / chondrocyte - found in cartilage

-c. Osteoblast / osteocyte - found in bone

-d. Hemocytoblast (hemopoeitic stem cell) - blood forming cell

4. Other cell types - adipose cell; mobile cells; WBC; mast cells; macrophage

Connective tissue overview

1. Mesenchyme – star shaped cells; embryonic; all others derived

2. Connective tissue proper – not bone, cartilage, or blood

-a. Loose connective tissue – areolar, adipose, and reticular

-b. Dense connective tissue – dense regular and dense irregular

3. Cartilage – very resilient; much water; no nerve supply; 3 types

-a. Perichondrium - well vascularized dense irregular; surrounds and nourishes

-b. Avascular - no blood vessels

-c. Chondroblast - chief cell type which produces the extracellular matrix

-d. Extracellular matrix - contains much water allowing it to be very flexible

-e. Lacunae - small pits in matrix in which chondrocytes reside

4. Bone – osteocytes; most support

5. Blood – red and white blood cells

Types of Connective Tissue

Mesenchyme

1. Description - gel ground substance; star shaped mesenchymal cells; fine fibers

2. Location – embryo; some remains to provide new cells in mature tissue

3. Function – all other connective tissue is derived from it

Areolar connective tissue

1. Description - gel-like matrix; all fiber types; fibroblast; other cells

2. Location – widely distributed under epithelium

-a. Lamina propria – it mucus membranes

3. Function - cushions organs, inflammation, retains and conveys fluid

Adipose tissue

1. Description - matrix sparse but similar to areolar; well vascularized

-a. Adipocyte - large fat droplet; nucleus and cytoplasm squeezed into a ring

2. Location - mostly under skin; around kidneys and eyes; abdomen and hips

3. Functions - fuel reserve; insulation; supports and cushions

Reticular connective tissue

1. Description - only reticular fiber; network; many reticular cells; vascularized

2. Location - lymphoid organs; lymph nodes, spleen, and bone marrow

3. Function - forms stroma (frame work) of lymphoid organs; many lymphocytes

Dense regular connective tissue

1. Description - mostly collagen fibers, some elastic fibers, one direction; wavy

-a. vascularization - poorly vascularized

-b. Elastic connective tissue – more elastic fibers (some ligaments)

2. Location - tendons (muscle to bone) and ligaments (bone to bone)

3. Function - great tensile strength when pulled in one direction

Dense irregular connective tissue

1. Description - mostly collagen fibers, some elastic fibers, many different directions

-a. Vascularization – poorly vascularized

2. Location - dermis of skin; fibrous capsule of organs and joints

3. Function - can withstand tension in many directions

Hyaline cartilage

1. Description - collagen fibers form unseen network; chondrocytes in lacunae

2. Location - costal cartilage; embryonic skeleton; end of long bones, trachea, larynx

3. Function - firm support with some pliability

Elastic cartilage

1. Description - like hyaline cartilage but more elastic fibers

2. Location - external ear and epiglottis

3. Function - allows great flexibility of structure

Fibrocartilage

1. Description - like hyaline but with apparent collagen fibers; one direction

2. Location - intervertebral disc; disc of knee joint

3. Function - able to absorb compressive shock

Bone (osseous tissue)

1. Description - hard matrix; many collagen fibers; osteocytes, lacunae; vascularized

2. Location - bones of the skeletal system

3. Function - support, protection, movement, storage calcium, blood cell formation

Blood

EPITHELIAL MEMBRANES

General

1. Epithelial membranes – epithelium and underlying layer of connective tissue

2. Location – where the sheet (membrane) is located

Cutaneous membrane

1. Skin - dry membrane

2. Epidermis - keratinized stratified squamous epithelium; top layer of dead cells

3. Dermis - thick layer of dense irregular connective tissue

Mucus membranes

1. Mucosae - wet membrane; respiratory, digestive, urinary, and repro systems

2. Epithelium - usually stratified squamous or simple columnar

3. Lamina propria - underlying layer of connective tissue (areolar connective tissue)

Serous membrane

1. Serosae - moist membranes found in the ventral body cavities

2. Double layered membrane – folded on itself

-a. Parietal layer - lines the cavity wall

-b. Visceral layer - lines the organ; continuous with the parietal layer; reflects back

3. Serous fluid - lubricant between layers; filtrate from blood in connective tissue

4. Mesothelium - simple squamous epithelium; enriches fluid

5. Areolar connective tissue - the connective tissue component

OTHER TISSUES

Nervous tissue

1. Description – made up of 2 different types of cells

-a. Neurons - branched or stellate cells which generate and conduct nerve impulses

-b. Supporting cells - nonconducting cells which support, insulate, and protect

2. Location - brain, spinal cord, and nerves

3. Function - transmits electrical signals from sensors and to effectors

Muscle Tissue

General

1. Cellularity - highly

2. Vascularized - well

3. Myofilaments - elaborate versions of the contractile proteins actin and myosin

Skeletal muscle

1. Description - long, cylindrical, multinucleated cells; obvious striations (stripes)

2. Location - attached to bone and sometimes to skin

3. Function - movement and facial expression

-a. Voluntary – under conscious control; not always; posture

Cardiac muscle

1. Description - branching, striated, uninuclear; interdiginate at intercalated disc

2. Location - walls of the heart

3. Function - propels the blood in the cardiovascular system

-a. Involuntary – not conscious

Smooth muscle

1. Description - spindle shaped, central nucleus, form sheets

2. Location - walls of hollow organs

3. Function - propels substances and objects

-a. Involuntary – not conscious