Vert. Zoology 2

Tissue

• a group of cells that work together to perform a common function

Four major tissue types

1. Epithelial tissue

   1. covering and lining of the body

2. Connective tissue

   1. bone and cartilage

3. Muscle tissue

   1. movement

4. Nerve tissue

   1. communication and coordination

Epithelial tissue

• highly cellular

• little or no intercellular space

• highly regenerative (mitosis)

• avascular

avascular

• little blood vessels

Connective Tissue

• lots of intercellular space

• ability to produce fiber to plug

• up holes = fibrosis —> repair process

Free apical surface

• faces lumen or external surface

  • cilia

  • microvilli

Cilia

• hair-like projections for movement

Microvilli

• fingerlike extensions of the cell membrane which increase surface

Lateral adherences

• structures which hold cells together

Types of lateral adherences

1. Right junctions

2. Desmosomes

3. Gap junctions

Tight junctions

• protein that links cells together which are impermeable

  • example: stomach, urinary bladder

Desmosomes

• protein attached cells that allow the cells to stretch without separating

  • example: cells of the heart

Gap junctions

• protein attaching cells that allows communication between the cells

  • example: nerve impulse

  • allows passage between cells

Basal surface

• (with basement membrane)

• regulates what passes

Three epithelial cell shapes

1. squamous cells

2. cuboidal cells

3. columnar cells

Squamous cells

• flat, scale like

• Nucleus looks like a flattened disc

• allows for rapid passage of substances

Cuboidal cells

• about as tall as it is wide; boxlike

• Nucleus is spherical

• many have microvilli

• function in secretion or absorption

Columnar cells

• taller than they are wide

• Nucleus is elongated top to bottom

• many have cilia or microvilli

• specialized function for secretion and absorption

Type of epithelial layers

1. Simple

2. Stratified

“Simple” means. . .

simple layer

“Stratified” means. . .

• multiple layers

• named by apical cell shape

Types of simple epithelia

1. Simple squamous epithelium

2. Simple cuboidal epithelium

3. Simple columnar epithelium

4. Pseudostratified columnar epithelium

Types of Stratified Epithelia

1. Stratified squamous

2. Stratified columnar

3. Stratified cuboidal

4. Transitional epithelium

Simple squamous epithelium

• flattened cells and found in the lungs

• lines body cavities and vessels

• alveoli of lungs

Simple cuboidal epithelium

• single layer, tall as they are wide

• found in ducts

• vertebrate kidneys and glands

Simple columnar epithelium

• single layered, taller than they are wide

• lines the digestive tract (SI, LI)

Pseudostratified columnar epithelium

• “pseudo” = false

• “stratified” = multiple layers

• gives us a false appearance of having multiple layers because the nucleus is of different heights

• respiratory tract (trachea)

Stratified squamous epithelium

• protective, multiple layers with flat apical cells

  • skin, mouth, and esophagus

• epidermis of birds, reptiles

  • shed molting in snakes

Stratified columnar epithelium

• multi-layer surface that is columnar

• rare

  • found in pharynx, white of eye, and salivary gland duct

Stratified cuboidal epithelium

• multiple layer and cuboidal shape

• found in glands of vertebrates and epidermis of some salamanders

Transitional epithelium

• can appear squamous or cuboidal

• found in bladder and ducts of urinary system

• can change shape from the state of organ

  • usually deals with piss

Glandular epithelia

• specialized to secrete product

Types of glandular epithelia

1. Endocrine

2. Exocrine

   1. Merocrine glands

   2. Holocrine glands

Exocrine

• glands with ducts that collect and carry product away from gland

Endocrine

• secrete product into extracellular fluid and is transported by the circulatory system

Functional Classification of Epithelial

1. Sensory

2. Germinal

3. Cuticular

4. Glandular

Sensory epithelial cells

• modified epithelial cells that detect changes in the environment

Germinal epithelial cells

• found in ovary and seminiferous tubules

Cuticular epithelial cells

• outermost layer of dead protective skin

Glandular epithelial cells

• secretes sweat, mucus, and enzymes

Four Categories of Connective Tissue

1. connective tissue proper

2. cartilage

3. bone

4. liquid (or blood)

“Fibro” means. . .

• connective tissue proper

“Blast” means. . .

• immature cell

• makes matrix

• responsible for making specialized cells

“cyte” means. . .

• mature cells that maintain the matrix