lecture 4b: Sketeal Anatomy

Question 1

What are the 2 components of the skeleton called?

Answer 1

Axial and Appendicular

Question 2

What parts of the skeleton contribute to the axial component?

Answer 2

Vertebral column, ribs, sternum

Question 3

What parts of the skeleton contribute to the appendicular component?

Answer 3

Fore limbs, hind limbs, pelvic components

Question 4

List six functions of the skeleton?

Answer 4

1. Protect and support soft tissues/organs
2. Attachment points for ligament and tendons
3. Contribute to body shape
4. Generate precursors of certain blood cels
5. Store lipids and minerals (ie: iron, calcium, etc) - may aid in buoyancy control
6. Properties of skeleton could provide time lien (after death) for biochemical events or stressors, pollutants.

Question 5

How do the vertebral column different between marine mammals?

Answer 5

Pinnipeds, sea otters, polar bears: cervical, thoracic, lumbar, sacral, caudal
Cetaceans, sirenia = cervical (7), thoracic, lumbar, caudal
(NO sacral)

Question 6

Cervical Vertebrae:

How many cervical vertebrae are usually found in marine mammals? Except what species? what one has fusion?

Answer 6

7, except sirenians have 6
Cetaceans (most) have fused of 2 or more vertebrae
Seals and sea lions have short necks but allows them to form an S - like curve.
Narwhals, beluga, river dolphins, blue whales = unfused allowing for neck mobility.

Question 7

Skeleton anatomy: Vertebral column

What part varies in length and why?

Answer 7

Thoracic and lumbar varies

Sacral 2-5 with some exceptions and ht e caudal vary depending on the length of the tail

Question 8

Skeleton anatomy: Vertebral column –>Lumbar vertebrae
Do they have rib attachments?
Which direction has better flexion and why?

Answer 8

Not attachment they are angled backward and extend past the tips of some lumbar vertebrae
Dorsoventral movements than in lateral ones. (Poss due to constraints from ribs angling back)

Question 9

Skeleton anatomy: Vertebral column –> sacral vertebrae

Who has, who does not and why?

Answer 9

Pinnipeds, polar bears and sea otters

No sacral vertebrae = cetaceans and manatees

Question 10

Skeleton anatomy: Vertebral column –> caudal vertebrae

1) Where?
2) Numbers? (Examples)
3) Role?

Answer 10

1) normal found within the tail
2) varies depending on the length of the tail
Ex: Manatees 22-27, cetaceans 13-49 (caudal fin contends to the notch of the fluke and NOT into the flukes themselves)
3) locomotion (in aquatic species –> whales, dolphins) while unimportant for polar bears and Pinnipeds.

Question 11

What are the major parts of the vertebrae?
Draw them out
(6)

Answer 11

1. Neural spine: used as level for muscles to flex tail
2. Neural arch: forms neural canals
3. Neural canal: where the spinal cord passes through and its protected
4. Centrum: main body primary support of vertebral column
5. Intervertebral disc: resists compression, adds flexibility and prevents vertebrae rubbing
6. transverse process: attachment points and protection soft tissue.

Question 12

What is a true rib?

Answer 12

Any of the ribs that are attached to the sternum by coastal cartilage

Question 13

What are false ribs?

Answer 13

Any ribs more posterior not directly attached to sternum

Question 14

What are floating ribs?

Answer 14

Most posterior ribs, NOT attached

Question 15

Skeletal Anatomy (Axial): Pinnipeds
what is notable about their vertebrae overall? And which regions is this especially found?

Answer 15

Have very large vertebrate (bones making up the spinal column) especially in the cervical area and the lumbar area

Question 16

Skeletal Anatomy (Axial): Pinnipeds
What does this notable regions allow for? What advantages is this on land? (Compare vertebrae in pinnipeds vs. Human; compare their size and shapes)

Answer 16

Allows for their extensive and strong movements of their head and hind limbs and help to maintain balance while walking on land.
Phocids have longer transverse processes in lumbar and is more compact
Otariid have med. compact while there cervical and thoracic spinous process are longer.

Question 17

Skeletal Anatomy (Axial): Pinnipeds
Which vertebrae do their ribs attach to?
Describe the 3 types of ribs and heir numbers for pinnipeds in general?

Answer 17

Ribs are firmly articulated (moving) to the thoracic vertebrae
8 true rubs, 4 false ribs, and 3 floating ribs.

Question 18

Skeletal Anatomy (Axial): Cetaceans 
Do they have the same number of cervical vertebrae? What is this number

Answer 18

Yes, they all have 7

Question 19

Skeletal Anatomy (Axial): Cetaceans 
What is unique about cervical vertebrae in cetaceans?

Answer 19

Depending on the species there may be 2 or more of these vertebrae fused

Question 20

Skeletal Anatomy (Axial): cetaceans 
Contracts cervical vertebrae between sperm whales and beluga whales and what, in each species, this results in functionally?

Answer 20

Sperm whale had a large number of fused vertebrae – >short rightist necks –> streamlines body and stabilizes head
Beluga whales –> less fused vertebrae –> more flexibility

Question 21

Skeletal Anatomy (Axial): Cetaceans

1) Describe their association with the thoracic vertebrae?
2) Describe the differences in eternal ribs between mysticeti vs. Odontoceti

Answer 21

1) are poorly articulated with the thoracic vertebrae
2) odontoceti: well defined bony eternal ribs
Mysticeti: hardly any distinct eternal rubs and are cartilage

Question 22

Skeletal Anatomy (Axial): Articular Facets

1) what are they?
2) where exactly are they located?
3) What purpose do they serve? What movement does it allow?

Answer 22

1) points of attachment for neck muscles
2) on the vertebrae along the entire vertebrae column
3) contra in or prevent certain motions between vertebrae thereby preventing rubbing but also allows for certain movements such as twisting or side to side movements

Question 23

Skeletal Anatomy (Axial): Subdermal CT sheath

1) what is this?
2) where is it located?
3) describe its structure and tissue type?
4) what purpose does it serve?

Answer 23

1) its a unique feature found in cetaceans
2) located along the thoracic and lumbar vertebrae
3) composed f strong cross hatched collagenous sheath that gives rigidity to the thorax
4) provides a very large surface for the muscles of the tail to attach to which provides rapid and powerful thrusts

Question 24

Skeletal Anatomy (Axial): Caudal Vertebrae
What and where are these found?

Answer 24

Chevron bones--> 2 bones that form a V (often fused ventrally) --> which forms a heal canal (carries and protects caudal arteries and beings to tail) 
Intervertebral ventrally (separate from vertebrae)

Question 25

Skeletal Anatomy (axial): caudal Vertebrae
Compare their number between cetaceans and manatees

Answer 25

Cetaceans = 13-49
Sirenians = 22-27

Question 26

Skeletal Anatomy (axial): caudal Vertebrae
What role do they play? Is this different for the differing marine species?

Answer 26

Prevents occlusion when tail flexed
Added attachments for muscle and stability and strength for hypoxia muscles or ventral flexion
Locomotion!!!

Question 27

Skeletal Anatomy (axial):  Cetacean Caudal Fin
How many flukes?

Answer 27

2 flukes

Question 28

Skeletal Anatomy (axial):  Cetacean Caudal Fin
Describe the layers of tissue beginning from blubber and working inwards?

Answer 28

Very thin layer of blubber, specialized system of BV, a layer of tough ligaments and a core of tough and dense fibrous tissue and is supported by very small compressed vertebrae that extend almost to the fluke notch

Question 29

Skeletal Anatomy (axial):  Cetacean Caudal Fin
How is this supported?

Answer 29

Supported by the thorax which allowed for muscles of the tail to attach

Question 30

Skeletal Anatomy (axial):  Cetacean Caudal Fin
Describe the vascularization to the caudal fin and its uniqueness

Answer 30

Penetrating the fibrous core is a system of BV that are arranged as heat retaining counter current system

Question 31

Skeletal Anatomy (axial):  Sirenians
Describe their thoracic and lumbar regions regarding relative length

Answer 31

Longer thorax – >shortened lumbar region

Question 32

Skeletal Anatomy (axial):  Sirenians
Describe their sternum and how it different from other mammals? how many ribs actually join the sternum?

Answer 32

Sternum in both manatees and dugongs is composed of a single broad flat bone with NO fused elements as normally found in other mammals.
Only the first 3 ribs attach to sternum, rest are free floating

Question 33

Skeletal Anatomy (axial): Sea Otters
Compared to river otters contrast their necks…
What does this accomplish functionally and structurally?
Describe the impact on rest of vertebral sections.

Answer 33

Shorter neck in relation to their trunk/body vs. River otter

Gives more attachment points for muscles bundles and thereby increasing rapid locomotion and varied movement in water.

Question 34

Skeletal Anatomy (axial):  Sea Otters
What is the impact of these adaptation to the animals ability ot move in water?

Answer 34

Allows for a streamlining of the sea otter body and the development of the thoracic, lumbar and caudal vertebrae regions

Question 35

Skeletal Anatomy (axial):  Sea Otters
how many pairs of ribs do sea otters have and which of these are attached loosely to sternum? What does this permit?

Answer 35

14 pair ribs; first 10 loosely articulating with sternum = mobility in thoracic area.

Question 36

Skeletal Anatomy (axial):  Polar Bears
- describe their skeletal adaptations to swim in water

Answer 36

Not very well adapted to swim in water as a result they have LITTLE SPECIAL SKELETAL ADAPTATIONS for aquatic locomotion

Question 37

Skeletal Anatomy (axial):  Polar Bears
What do they rely on when swimming?

Answer 37

Relying on brute strength and stamina when swimming

Question 38

Skeletal Anatomy (axial):  Polar Bears
Describe their necks and purpose

Answer 38

Long necks = more strong muscles to attack and haul out prey