Tissue Basics

Question 1

What is a tissue?

Answer 1

• An aggregation of cells and intercellular substances specialized to perform particular functions
• Tissu= woven. Texo= to weave

Question 2

What is an organ?

Answer 2

A more complex structure that is comprised of different arrangements of the four basic tissues

Question 3

What are the four basic tissues?

Answer 3

1. Epithelium
2. Connective
3. Muscle
4. Nervous

**All organs are various arrangements of all or a mix of some of these tissues. Identification of tissues can be achieved by identifying the presence of specific features/components of cells, and their relationships

Question 4

Embryonic origins of the 4 basic tissues

Answer 4

1. Endoderm
2. Mesoderm
3. Ectoderm

Question 5

Endoderm

Answer 5

• Inside layer, forms epithelium

Examples: Respiratory epithelium, gastrointestinal epithelium, liver, pancreas and gall bladder glandular epithelium, thyroid, parathyroid, thymus, tympanic cavity, auditory tubes

Question 6

Mesoderm

Answer 6

• Middle layer
• Almost all of the connective tissues: Skeletal, cardiac, smooth muscle

Examples: Epithelium of the kidney and gonads, mesothelium of the pluera, peritoneum and pericardium, endothelium, adrenal cortex, seminiferous tubules, genital duct

Question 7

Ectoderm

Answer 7

• Outer layer
• Surface ectoderm: epidermis, cornea and lens epithelia, inner ear, anterior pituitary
• Neuroectoderm: central and peripheral nervous system

Question 8

Epithelial cell types

Answer 8

Classified based on shape.

1. Squamous cells
2. Cuboidal cells
3. Columnar cells

Question 9

Types of surface epithelia

Answer 9

1. Simple
2. Pseudostratified
3. Stratified (2 layers)
4. Sensory epithelium

Question 10

Types of simple surface epithelia

Answer 10

1. simple squamous
2. simple cuboidal
3. simple columnar

Question 11

Types of pseudostratified surface epithelia

Answer 11

1. pseudostratified columnar (mix of columnar and cuboidal so apparat’s like stratified but actually simple with different sized cells; all cells touching bottom)
2. Transitional (mixture of squamous and cuboidal cells)

Question 12

Types of stratified surface epithelia

Answer 12

1. stratified squamous
2. stratified cuboidal
3. stratified columnar

Question 13

Sensory epithelium

Answer 13

Layers of sensory and supportive cells in the retina, internal ear, olfactory mucosa, and taste buds

Question 14

Where are transitional epithelia found?

Answer 14

In areas that need to stretch and unstretch

Ex. urinary organs