Presentation 8: Axial Skeleton

Question 1

Axial Skeleton

Answer 1

Vertebral column, Skull, Thoracic Cage (chest)

Question 2

Centrum

Answer 2

Notochord ossifies to form main body of vertebrae (centrum) with two main parts, intercentrum dominant and pleurocentrum dominant.

Question 3

Intercentrum dominant

Answer 3

Anterior and slightly ventral structure surrounding the notochord, no longer in living amniotes but present in extinct amphibians

Question 4

Pleurocentrum dominant

Answer 4

Posterior and slightly dorsal structure, in living amniotes, pleurocentrum is dominant in living amniotes

Question 5

Neural Arches

Answer 5

2 Bars that connect dorsally (at the Neural Spine) to form the Neural Canal

Question 6

Neural Canal

Answer 6

Canal above the notochord and centrum formed by the 2 neural arches. Protects the spinal chord.

Question 7

Neural Spine

Answer 7

Where the 2 neural arches fuse dorsally

Question 8

Hemal Arches

Answer 8

Present only in posterior vertebrae, 2 bars that extend ventrally under the notochord and centrum and connect ventrally together at the Hemal Spine forming the Hemal Canal

Question 9

Hemal Spine

Answer 9

Connection of Hemal Arches present in posterior vertebrae that form the Hemal Canal (= chevron bones in amniota)

Question 10

Hemal Canal

Answer 10

Created by the Hemal Arches connecting ventrally at the Hemal Spine

Question 11

Processes of Centrum

Answer 11

Apophyses (include Parapophyses, Diapophyses, and Hypapophyses)

Question 12

Parapophyses

Answer 12

One of the processes of centrum - Slightly ventral on vertebrae

Question 13

Diapophyses

Answer 13

One of the processes of centrum - (aka transverse processes) extends to sides to articulate with the tuberculum of the rib (capitulum of rib connects to ventral side of centrum)

Question 14

Hypapophyses

Answer 14

One of the processes of centrum - mostly found in fossils, not necessarily in living organisms today

Question 15

Processes of Neural Arches

Answer 15

Zygapophyses (Include Prezygapophyses and Postzygapophyses)

Question 16

Prezygapophyses

Answer 16

One of the processes of neural arches -(aka anterior processes) extends slightly forwards/dorsally - smooth surface faces each other)

Question 17

Postzygapophyses

Answer 17

One of the processes of neural arches -(aka posterior processes) extends slightly backwards / ventrally - smooth surface faces away

Question 18

Hypomere

Answer 18

Embryonic mesoderm section
differentiates somatic and splanchnic layers
somatic layer gives rise to outside muscles while
splanchinc layer gives rise to muscles around organs

Question 19

Embryonic mesoderm sections

Answer 19

Epimere (dorsal somite)
Mesomere (gives rise to urogenital organs)
Hypomere (differentiates somatic and splanchnic layers - somatic layer gives rise to outside muscles while splanchinc layer gives rise to muscles around organs)

Question 20

Mesomere

Answer 20

Embryonic mesoderm section
gives rise to urogenital organs

Question 21

Epimere

Answer 21

Embryonic mesoderm section
(dorsal somite) divides into dermatome, myotome, and sclerotome which gives rise to dermis, muscle formation, and vertebrae respectively

Question 22

Dermatome

Answer 22

Epimere section
Gives rise to the dermis

Question 23

Myotome

Answer 23

Epimere section
Contributes to muscle formation

Question 24

Sclerotome

Answer 24

Epimere section
gives rise to vertebrae (sheet around the notochord aka perichordial tube, posterior/caudal part of flanking sclerotome thickens, more cell density, & caudal half of one sclerotome attaches to cranial half of the next sclerotome)

Question 25

Vertebral Column Development ( 5 steps)

Answer 25

1. Embryonic mesoderm divides into epimere, mesomere, and hypomere 2. Epimere divides into dermatome, myotome, and sclerotome 3. Vertebrae are intersegmental in relation to the primary segmentation of the mytomes (neural and hemal arches associated w/ anterior part (caudal halves), spinal ganglia line up with posterial cranial part, blood vessels line up withe middle part. 4. When it is all lined up, chondrification begins (formation of cartilage) 5. Cartilage is continuous for a short period when spinal ganglia, notochord, and myotomes induce breaks before ossification begins and then individual vertebrae are established

Question 26

Classification of Vertebrae ( 4 options)

Answer 26

Opistocoelous (anterior convexity + posterior concavity) Procoelous (anterior concavity + posterior convexity) Amphiocoelous (concavity both anteriorly and posteriorly) Acoelous (no concaves, both sides flat)

Question 27

Opistocoelous

Answer 27

Classification of Vertebrae (anterior convexity + posterior concavity)

Question 28

Procoelous

Answer 28

Classification of Vertebrae (anterior concavity + posterior convexity)

Question 29

Amphiocoelous

Answer 29

Classification of Vertebrae (concavity both anteriorly and posteriorly)

Question 30

Acoelous

Answer 30

Classification of Vertebrae (not concave, both sides flat)

Question 31

Specialization of Amphibia Vertebrae

Answer 31

1st vertebrae differentiates into atlas (specialized to articulate w/ occipital arch) Trunk vertebrae Single Sacral Vertebrae which articulates with the pelvic girdle and connects to Illium Several caudal vertebrae remain in tail for salamanders Caudal vertebrae of frogs fuse into urostyle

Question 32

Specialization of Amniota Vertebrae

Answer 32

pleurocentrum makes up bulk of the vertebral column Strong zygopophyses 1st cervical vertebrae - atlas 2nd cervical vertebrae - axis (both 1st and 2nd cervical vertebrae support head) Types of Vertebrae 1. Cervical (distinguished neck) 2. Thoracic (associated with ribs) 3. Lumbar (posterior section) 4. Sacral (at articulation w/ posterior limbs) 5. Caudal (all vertebrae in the tail)

Question 33

Diversity of Vertebrae in Amniota - BIRDS

Answer 33

BIRDS: Sternum = highly enlarged + durable to support breast muscles for flying Last 4 caudal vertebrae fuse to form the pygostyle Synsacrum present Unicate process (enlarged sternum for flight) part of RIBS

Question 34

Diversity of Vertebrae in Amniota - MAMMALS (2 main points)

Answer 34

MAMMALS: 1. 20 Trunk vertebrae that divide into thoracic vertebrae and lumbar vertebrae 2. 3 of sacral vertebrae fuse

Question 35

Types of Vertebrae in Amniota (5 types)

Answer 35

Types of Vertebrae 1. Cervical (distinguished neck) 2. Thoracic (associated with ribs) 3. Lumbar (posterior section) 4. Sacral (at articulation w/ posterior limbs) 5. Caudal (all vertebrae in the tail)

Question 36

Fish Ribs (2 types)

Answer 36

Dorsal Rib: intermuscular the junction of the myoseptum and the horizontal septum Septa are made of connective tissue Horizontal septum separates epaxial (dorsal) and hypaxial (ventral) muscles Ventral Rib - Pleural (subperitoneal) at junction of the myoseptum and peritoneum

Question 37

Tetrapod Ribs - ancestral and later condition

Answer 37

1. Ancestrally bicapitate (Tuberculum articulates with diapophyses and Capitulum articulates with paraphophyses) 2. Later unicapitate

Question 38

Amniota Ribs (2 types) and function

Answer 38

Ribs: thorax: costal rib (ossified) and sternal rib (cartilaginous) - ribs participate in respiration by enabling expansion while protecting the lungs

Question 39

Sternum (amphibians, amniotes, lizards, turtles snakes and gymnophiona, mammals, and birds)

Answer 39

- amphibian sternum not homologous to amniote sternum - Amniotes : ventral midline structure - turtles snakes and gymnophiona : sternum absent - lizards: either cartilaginous or bony - mammals: composed of several elements - birds: enlarged for attatchment of flight muscles

Question 40

Mammalian Sternum Components

Answer 40

1. Manubrium 2. Body 3. Xiphoid process