Tissues

The four principle tissue types?

1. Epithelia

2. Connective

3. Muscle

4. Nervous

1. Epithelial tissue

Largely found in two forms:

coverings and lining epithelium, glandular epithelium

The six major characteristics?

1. cellularity

2. polarity

3. attachment

4. avascularity

5. innervation

6. regeneration

1. Cellularity

• composed entirely of cells bound very tightly together

• very little extracellular matrix (space outside the cell)

2. Polarity

- Apical surface:

free surface exposed to external enviorment or internal body space

Lateral Surface:

forms the intercellular junction

Basal Surface :

surface that is attachted to underlying connective tissue

3. Attachment

• basal surface is attached to basement membrane

• basement membrane composed of both the epithelium and supporting connective tissue cells

4. Avascularity

• no blood vessels are present

• nutrients received from diffusion from basement membrane or connective tissue

5. Innervation

• connected to nerves to allow sensory detection

6. High regeneration capacity

• basal stem cells are always replacing damaged apical cells

Functions of epithelial tissue?

protection

from dehydration and abrasion

selective permeability

select things are able to penetrate at the borders

secretions

glands produce secretions such as sweat

Sensations

pressure, eye for vision, tounge for taste

Classification of Epithelia

1. number of epithelia cell layers

2. shape of the cell at the apical surface ie structure

Simple epithelium?

Stratified epi?

Pseudostratified epi?

• one layer of cells

• two or more layers

• single layer of cells with nuclei

Squamous?

Cuboidal?

Columnar?

Transitional?

• cells are flat, wide with a flattened disc-like nucleus

• cells are as tall as they are wide with spherical nucleus

• they are taller than wide with oval shaped nucleus

• change shape depending on stretch ie umbrella shaped

simple squamos epithelium

description: single layer of flattened cells

Location: lungs and blood vessels

Function: diffusion, osmosis and filtration

special names of simple squamos epi

Endothelium:

blood vessels and heart

Mesothelium

serous membranes

Simple cuboidal epithelium

• description: single layer

• location: kidney tubules, surface of ovary, thyroid glands

• function: absorption and secretion

Simple columnar epithelium

description: single layer

• associated with goblet cells for mucus production

• associated with microvilli

location: digestive tract and uterine tubes

function: ideal for absorption or secretion

stratified squamous epithelium:

1. Non-Keratinized stratified squamous epithelium

description: moist layers of live squamous cells due to saliva or mucus

location: mouth, pharynx, esophagus, vagina, anus

function: protection against abrasion

how many forms of stratified squamous epithelium is there?

two

stratified squamous epithelium:

2. Keratinized stratified squamous epithelium

description: keratin is heavily expressed in the cells

• cells at the apical surface are dead and are filled with tough keratin

location: epidermis of skin

function: protection against abrasion

pseudostratified columnar epithelium

description: single layer cells are Different heights with No cilia

all cells touch the basement membrane but only tall columnar cells reach apical surface

Pseudostratified columnar epithelium

1. non-ciliated pseudostratified columanr epi cells

• non ciliated

location: male vas deferens and epididymis

Pseudostratified columnar epithelium

2. ciliated pseudostratified columnar epi cells

description: single layer

• may house goblet cells which make mucin

location: respiratory tract

function: secretion and directional movements of particulates

transitional epithelium

description: varies in appearance based on stretch

• apical cells may appear squamous like or rounded like an umbrella

• basal cells are always cuboidal

location: urinary bladder, ureters, urethra ie places that stretch

function: allows for expansion of lumen

functions of connective tissue?

• physical protection

• support and structural framework

• bindings structures

• storage

• transport

• immune protection

Classification of connective tissue?

connective tissue proper

• loose and dense

supporting connective tissue

• cartilage

• bone

fluid connective tissue

• blood

Cells of connective tissue?

• Fibroblasts: cells of CT proper

  synthesizes collagen fibers

• Chondrocytes: cells of cartilage

  synthesizes cartilage fibers

• Adipocytes: cells of adipose tissue

  store energy as fat

• Osteocytes: cells of bones

  synthesize the matrix of bone tissue

• Erythrocytes: red blood cells

Fibers of connective tissue

• collagen fibers:

  • resist tension

  • found in tendons and ligaments

• Elastic fibers:

  • stretch easily and recoil

  • found in lungs and arteries

• Reticular fibers:

  • interwoven network of fibers

  • found in lymph nodes, liver, spleen

Dense Connective tissue

• primarily of densely packed protein fibers

• collagen fibers are the dominant fiber type

Dense Regular CT

Description: densely packed and parallel collagen fibers

fibers are aligned along direction of stress

location: tendons and ligaments

function: resist stress in one direction

Elastic CT

description: dominated by elastic fibers

location: vocal cords, large and medium arteries, ligaments of spinal column, trachea

function: resilience and recoil

loose connective tissue

• loose arrangements of protein fibers with few cells

• occupies spaces between and around organs to act as a packing material

Areolar CT

description: loose array of collagen, elastic and reticular fibers

plentiful blood vessels

many fibroblasts

location: surrounds BV; subcutaneous layer; lamina propria of mucous

function: packing material between other tissues; wraps BV nerves; cushions organs

Adipose CT

description: commonly referred to as fat

consists primarily of adipocytes filled with lipids or fat

location: orbit, breast subcutaneous layer

function: cushion and heat insulation

Reticular CT

description: meshwork of reticular fibers, fibroblasts and leukocytes

location: spleen, lymph nodes, liver

function: form a scaffolding for other cells

Cartilage

Characteristics:

• firm, gel like matrix

• contains chondrocytes in lacunae

• strong and resilient due to collagen and elastic fibers

• avascular

Types of Cartilage:

• hyaline, elastic and fibrocartilage

Hyaline Cartilage

Description: clear glassy appearance with chondrocyte without lacunae

• most common but weakest

location: fetal skeleton, nose, trachea, larynx, costal cartilage

function: supports flexibility and strength

Elastic cartilage

description: contains numerous elastic fibers

• elastic fibers form web like mesh around chondrocytes

location: epiglottis external ear

functions: extreme flexibility and resilience

Fibrocartilage

description: contains numerous coarse visible collagen fibers

• chondrocytes are scattered throughout

location: intervertebral disc, meniscus, pubic symphysis

function: shock absorber to resist compression

Bone tissue

makes up the mass of bone organ

more solid

Compact bone?

found in hard outer shell of bone

Spongy bone?

deep to compact bone

Compact Bone?

Haversian system (Osteon)

• cylindrical arrangement of compact bone tissue

• concentric rings of bone tissue called Lamellae

Spongy Bone

Bone tissue forms a latticework structure

• Trabeculae is made up of parallel lamellae

Blood?

RBCs- erythrocytes

WBC- leukocytes

matrix is plasma

types of muscle?

skeletal

smooth

cardiac

Skeletal muscle tissue

description: cylindrical muscle cells

multiple nuclei

striated

location: skeletal muscle

function: shorten to cause voluntary movements

cardiac muscle tissue

description: striated Y-branched fibers

location: walls of the heart

function: involuntary contraction (beat)

smooth muscle tissue

description: unstriated spindle

location: walls of viscera, stomach, bladder, BV

function: involuntarily

Nervous Tissue

found in brain, spinal cord and nerves

• neurons

• glial cells