Cells to Tissues

Question 1

Major tissue types in humans?

Answer 1

• connective tissue
• epithelial tissue
• nervous tissue
• muscle tissue

Question 2

What are epithelia?

Answer 2

• cover surfaces externally and line surfaces internally
• mainly involved in absorption, secretion and protection
• sheets of cells held together by basement membrane, held together by cell-to-cell junctions, no blood supply (rely on diffusion of 02, nutrients), little non-cellular material
• different types depending on where in body

Question 3

Simple squamous epithelium

Answer 3

• 1 layer
• very thin, large, flat
• minimal amount of barrier (lungs, gas exchange)
• vulnerable

Question 4

Simple cuboidal epithelium

Answer 4

• 1 layer
• well-shaped (lines ducts: ex. kidney tubules)
• not too much surface area but stronger than in lungs

Question 5

Simple columnar epithelium

Answer 5

• 1 layer
• strong
• large surface area for absorption, may be increased through microvilli on surface
• ex: gut

Question 6

Pseudostratified epithelium

Answer 6

• 1 layer (=simple!)
• looks as if made of multiple layers, actually just very different sized cells (but all of their membranes still in contact with basement membrane)
• abrasion and lubrication
• goblet cells secrete mucus, cilia move dust/particles

Question 7

Transitional epithelium

Answer 7

-stratified (multiple layers)
-cells of different sizes, fit together loosely
=stretchy
-ex: bladder, urinary tract (need to expand, go back)

Question 8

Stratified squamous epithelium

Answer 8

• found in areas prone to friction/abrasion
• big thick layer of cells which can proliferate if subject to stress = calluses/corn
• 2 forms
  
  • without keratin (tongue = taste, doesn’t tear mouth)
  • with keratin (skin = stronger)

Question 9

What are muscles?

Answer 9

• contractile tissue responsible for movement within body

- 3 types: smooth, striated/skeletal, cardiac

Question 10

Smooth muscle

Answer 10

• single cells containing single central nucleus
• not obviously striated
• not under voluntary control = slow to tire
• in walls of gut, urinary system, blood vessels, skin, resp. system, endocrine system

Question 11

Striated/skeletal muscle

Answer 11

-made up of fibres containing multiple nuclei
= a syncytium (not single cells)
-clearly striated
-voluntary (or reflex)
-fast contraction
-in muscles that move skeleton + diaphragm + upper part of esophagus
-does get tired

Question 12

Cardiac muscle

Answer 12

• single cells with single nucleus BUT linked to intercalated discs (junctions) that allow fast conduction
• striated
• not under voluntary control
• doesn’t tire
• found in wall of heart

Question 13

What are connective tissues?

Answer 13

• mostly for support or packing/wrapping
• cells surrounded by non-cellular tissue (matrix)
• 4 types: blood, loose connective tissue, bone, cartilage

Question 14

How are bones formed?

Answer 14

• Endochondral bone: replaces cartilage (ex. limb bones, vertebrae, skull base)
• Intramembranous bone: forms directly in membranes/skin in absence of cartilage (ex. skull)

Question 15

Types of cartilage?

Answer 15

• Hyaline cartilage (nose, joints)
• Elastic cartilage (in ears, flexibility)
• Fibrocartilage (between vertebrae, strength/durability/response to stress)