Skeletal System

Question 1

Three types of skeletons?

Answer 1

Hydrostatic
Exoskeleton
Endoskeleton

Question 2

Describe hydrostatic skeleton?

Answer 2

consists of muscle & fluid that helps provide support for the animal
no rigid support present (ie., bone or shell)
fluid can be squeezed within a compartment when muscles contract
the fluid is forced into the relaxed portion of the animal to extend, resulting in movement

Examples:
Cnidarians-jellyfish
Platyhelminthes-flatworms and tapeworms
Nematoda-round worms
Annelida-segmented earthworms

Question 3

Describe exoskeleton?
What two various?

Answer 3

rigid, external body covering
equivalent to a shell

variation:
Mollusca = CaCO3 shell
Arthropoda = chitinous cuticle

protects against predators and provides surface for muscles to attach and work against

Question 4

Endoskeleton primary function?

Answer 4

supports & maintains overall shape of body

storehouse for calcium (Ca2+) & phosphate ions (PO43-)

site of blood cell formation (hematopoiesis)

Question 5

What is the composition of bone?

Answer 5

70% of bone is hydroxyapatite (by weight)
Ca5(PO4)3OH

25% is organic material, including cartilage

remaining weight is due to water

Question 6

Two major regions of skeleton?

Answer 6

Axial
Appendicular

Question 7

Describe axial skeleton?

Answer 7

skull (cranial and facial bones), rib cage (sternum + 12 pairs ribs), vertebral column (24 bones)

Question 8

What is the appendicular skeleton?

Answer 8

all of the attached limbs, including the pectoral and pelvic girdles

Question 9

Two types of bone and what they are filled with?

Answer 9

Compact bone
Spongy bone
Bone marrow

Question 10

Describe compact bone?

Answer 10

consists of dense, compact bone regions:

typically found in the outer surfaces of bone

no space exists within this bone material other than microscopic canals

Helps provide strength & resists compression

Question 11

Describe the basic unit of compact bone?

Answer 11

Basic functional unit: osteon

Stacks of tiny cylinders each of which features tiny canals to supply nutrition to
mature bone cells called osteocytes

consist of concentric rings interconnected by tiny canals which supply nutrition to bone cells
mature bone cells are called osteocytes

Question 12

Describe spongy bone?

Answer 12

typically found in the interior of bones
features open spaces

Question 13

What does marrow contain?

Answer 13

contains adipose and white blood cells

Question 14

Describe three general regions of long bones?

Answer 14

a. diaphysis – shaft
b. Metaphysis (x2) – widening, interconnecting section between shaft and ends of bone
c. Epiphysis (x2) – ends of long bones

Question 15

What are the growth plates and what occurs there?

Answer 15

i. Location of cartilage where long bone growth occurs – epiphyseal (growth) plates
ii. Conversion of cartilage -> bony matrix is called ossification
iii. ossification in long bones begins in-utero; ossification doesn’t conclude until around 23
years of age

Question 16

When can bone no longer grow?

Answer 16

when ossification centers meet and the epiphyseal (growth) plate ossifies, bone can no longer grow in length

Question 17

bone can continue to grow in length if ____ cells remain active

Answer 17

cartilage

Question 18

What are the three major bone cell types and what do they do?

Answer 18

a. osteocyte – mature bone cell found in the lacunae of the osteon
b. osteoblast – responsible for depositing new bone mineral
c. osteoclast – demineralize bony matrix using acidic secretions

Question 19

How do osteoclasts function?

Answer 19

osteoclasts demineralize bony matrix using acidic secretions

Question 20

What does parathyroid hormone do?

Answer 20

Parathyroid hormone is secreted from parathyroid glands in response to low Ca2+ levels
a. Function:
i. Causes kidneys to reabsorb Ca2+
ii. Stimulates osteoclast activity in bones to release Ca2+
iii. Production of vitamin D to stimulate calcium absorption from digestive tract