Lecture 5A Flashcards
What are the bones present in the forelimbs (arms)
- Scapula
- humerus
- Radius/Ulna
Hand - Carpals
- metacarpals
- Phalanges
What are the bones present in the hindlimbs (legs)
- Pelvis
- Femur
- Tibia (front) /Fibula (back)
Foot (Pes) - Tarsals
- Metatarsals
- Phalanges
What are the three parts of the Pelvis?
What is the function of the Pelvis?
- Ilium
- Ischium
- Pubis
Function
- Transfer weight from limbs to rest of skeleton
- Protect lower organs
- Attachment for muscles
What is the acetabulum in the Pelvis?
- Acetabulum is the point where the head of the femur is placed
How is the forelimb of pinnipeds different from human forelimbs?
- Pinnipeds have wider and fatter bones
- Still consists of the same bones with same names
What is different about the fibula and tibia of a pinniped compared to a human?
- Fibula and tibia head are fused together
What does the various lengths and sizes of the bones determine?
- Surface area for muscle attachment points
- Depending on attachment of muscles, flexibility or strength of animal
Of the Pinniped species, which of the three can use its hind legs for locomotion?
- Otariidae
- Odobenidae
Phocidae CANNOT use its hind legs, drags them behind.
How are the forearms of Cetaceans different from humans
- Same bone names
- More flat bones
- more pronounced shape to allow for increased muscle attachment
Describe Hind limb structures in Cetaceans
- Lost ALL Bones for hind limbs
- Reduced vestigial pelvic bones
What is the composition of the tail in the cetacean? (4 things)
- very thin layer of blubber
- Layer of tough ligaments
- Dense fibrous tissue
- very Small compressed vertebrae (does not extend into the fluke)
What is unique regarding blood vessel arrangement in the tails of Cetaceans
- countercurrent arrangement retains heat
What is different regarding sirenian forelimbs compared to humans?
- same bones with same names
- different shapes and sizes
Describe the hind limbs in sirenians
- No hind limb bones
- Evolved OUT of sirenians
- Reduced vestigial pelvic bones
- Similar to Cetaceans
What is unique about the hind limbs of sea otters?
- Web of skin between the digits
- allows doubling of surface area when digits spread
- allows for increase surface area and propulsion
What is the difference between a sea otter and a river otter in terms of anatomy?
Smaller scapula
What adaptations has the polar bear skeletal anatomy taken on?
- Long necks = stronger muscles for hauling prey
- Large strong forelimbs
- feet that form flat plates (swimming)
What adaptations have cetaceans and sirenians made by living totally in the water?
- losing their hind limbs
- Compensate for boyancy control and propulsion
What adaptations have pinnipeds, sea otters, and polar bears made?
- improved modes of propulsion through water
- Live part of life on land
What are the four regions that the muscular system is divided into?
- Cranial
- Axial
- Thorax
- Fore and hind limbs
What is the main function of cranial muscles in marine mammals?
- Open the nares/blowholes
What are the functions of the sirenian facial muscles?
- muscles inserted into the snout
- very flexible, allow for food manipulation
How are facial muslces arranged in Cetaceans?
- Airsac system on forehead involved in sound production
- Mysticetes have facial muscles that extend the two halves of the mandible (squeezes and ingests food)
What muscle is present in terrestial mammals but not in cetaceans? (helps for suckling)
How do cetaceans adapt?
- Buccinator muscle
- Cetaceans have long snout and mother squirts milk into baby’s mouth by contraction of mammary glands
What is the composition and proportion of the tongue?
- Made of mainly skeletal muscles
- Almost the size of an elephant
- makes up about 2.5% body weight
How do cetacean’s mouth muscles differ from humans?
- Reduced temporal muscle
- Use 2 other muscles (Pterygoids and masseter) to open and close jaw
- Cannot move mouth side to side
What is the difference between sirenian neck muscles and cetacean neck muscles?
- Sirenians = long necks, very muscular, used for balancing the body during movement
- Cetaceans = very short necks
Epaxial and Hypaxial muscles create propulsion
What are the epaxial muscles in cetaceans?
- Longissimus (attached to subdermal sheath)
- Multifidus (attached to posterior thoracic and lumbar vertebrae)
- Contraction pulls tail up
- Muscles do not affect head position
Where is the cutaneous truci muscle and what is its purpose?
- Covers most of the thorax and abdomen
- Sirenians = very large and assists in downstroke of the tail
- Cetaceans = specialized and overlies the mammary gland to release milk
What muscles control the down stroke of the fluke in cetaceans?
Large hypaxialis lumborum
- Flexor caudae lateralis and medialis are extensions of this large set of muscles
How does the penis work in cetaceans?
- Not under muscular control
- retractor penis muscles can move the penis into a pouch in the body to maintain streamline shape
How are the forelimbs used in cetaceans?
- Forelimbs mainly used for stearing
- NOT propulsion
- movement is mainly adductive (in) and abductive (out)
What bone is missing in pinnipeds and cetaceans?
Clavicle
What are the forelimbs used for in Phocidae?
- Not used for propulsion
- little role for land locomotion
What are the forelimbs used for in Otariidae?
- Propulsive force
- land locomotion
What are the forelimbs used for in odobenidae?
- NOT propulsive force
- USED for land locomotion
What are the uses of the forelimbs in sirenians?
- NOT propulsive forces
- They do have movement in joints (Synovial joints)
- Forlimbs can manipulate food
Which pinniped species uses their hind limbs to move on land?
- Odobenidae
- Otaridae (hind limbs only for locomotion)
