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Comparative Anatomy 1 > Lecture 9 > Flashcards

Lecture 9 Flashcards

1
Q

List the subdivisions of the vertebrate skeletal system.

A

Vertebrates are characterized by an internal skeleton made of cartilage and/or bone. This internal framework can be divided into subdivisions as follows:
• Axial skeleton:
• Chondrocranium:
- Braincase and capsules for organs of special sense
• Viscerocranium:
- Gill arches and jaws
• Vertebral column
• Appendicular skeleton:
• Limb girdles (pectoral and pelvic)
• Limbs (forelimbs and hindlimbs, including fins

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2
Q

Describe vertebral column

A

The vertebral column of vertebrates is an obvious example of segmentation in vertebrates.
• The vertebral column consists of a series of segments called vertebrae as well as additional related structures.
• The vertebrae and related structures may be composed entirely of cartilage or bone or both.

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3
Q

Describe centrum

A
  • The centrum is typically a cylindrical structure that is connected to similar cylindrical centra both cranially and caudally.
  • This chain of centra replaces the notochord of the protochordates, such as amphioxus, as the principal axial support structure.
  • This chain of centra is flexible, but may not be as flexible as a notochord.
  • A flexible chain of centra would be useful for swimming, but would not be as useful for supporting a terrestrial life-style.
  • In many vertebrates (including humans) parts of the notochord may persist within and/or between adjacent vertebrae.
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4
Q

Describe neural arch

A
  • Sits on top of the centrum (dorsal surface) and provides a protective passageway for the spinal cord.
  • A neural spine often projects from the dorsum of the neural arch.
  • Provides lever arm for muscle attachment.
  • In Latimeria the neural spines are hollow and filled with cartilage – “coelacanth” means hollow spine.
  • A corresponding hemal arch is present on the ventral surface of the centrum of each of the caudal (tail) vertebrae.
  • A caudal artery and vein pass through the hemal arch.
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5
Q

Components of a shark vertebral column

A 
A Intercalary plate (fill in gaps between adjacent neural arches and protects spinal cord)
B Neural spine
C Neural arch
D Spinal cord
E Centrum of vertebra
F Caudal artery
G Caudal vein
H Hemal arch
I Hemal spine
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6
Q

Regional variations within vertebral column in fishes

A

• Precaudal vertebrae:
- Include all the more cranial vertebrae that lack a hemal arch
• Caudal vertebrae:
- Include all the vertebrae caudal to the precaudal
vertebrae
- Possess hemal arches

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7
Q

Vertebral column fishes

A

Centra tend to be more ossified.
• Each neural arch is topped by a long, slender neural spine.
• Prominent notochord instead of ossified centra are still retained in more primitive bony fishes such as the sturgeon.
• Pelvic and pectoral girdles are not tied into fish vertebral column.

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8
Q

Compartmentalization of vertebrate body

A
  • The vertebrate body plan is tied together by sheets of connective tissue referred to as myosepta.
  • The myosepta tie into the vertebral column.
  • Collectively, the myosepta form compartments in which are enclosed masses of skeletal muscle.
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9
Q

Vertebral Column: Early Tetrapods

A

Early tetrapod centrum developed from two parts:
• Intercentrum.
• Pleurocentrum.
• One or the other or both contributed to the formation of the centrum in early tetrapods.
• Vertebral column replaced notochord as the main axial support.
• Precaudal vertebrae became specialized (correlated with terrestriality):
• Cervical: articulated with skull
• Trunk: processes for rib attachment
• Sacral: articulated with pelvic girdle
• Pelvic girdle tied into vertebral column via ilia.

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10
Q

Describe vertebral column of Crossopterygians

A 
Each centrum consisted of:
• Single, larger intercentrum:
     - “U”-shaped and cranial
• Paired, smaller pleurocentra:
     - Caudal and dorsal to intercentrum
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11
Q

Describe vertebral column of Stereospondylous labyrinthodonts

A

Centrum entirely derived from

intercentrum

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12
Q

Describe vertebral column of Embolomerous labyrinthodonts

A

Intercentrum and pleurocentrum

equal in size.

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13
Q

Describe vertebral column of modern amphibians

A

Tendency in later tetrapods was to reduce:
- The intercentrum to a small,
cranial, ventral element to which attached the capitulum (head) of the rib.
- Considerably increase the size of
the pleurocentrum.
• In later tetrapods, notochord was
either completely eliminated in the adult or persisted as a slender rod passing through the pleurocentrum
or confined to spaces between intercentra.
• Uncertain in modern amphibians whether centrum is derived from pleurocentrum or intercentrum.

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14
Q

Vertebral column of salamanders

A

Regional variations within the vertebral column seem to be correlated with terrestriality.
• Specializations of precaudal vertebrae (First seen in primitive tetrapods):
• First precaudal vertebra = cervical vertebra
- Only one in amphibians
• Last precaudal vertebra = sacral vertebra
- Only one in amphibians
• Vertebrae between cervical and sacral are trunk vertebrae
- Numerous in salamanders
- Reduced to about six or seven in anurans
- Transverse processes have attachment sites for ribs.

  • Neural arches with short, blunt neural spines are located on the dorsal surfaces of the centra.
    • Caudal vertebrae in salamanders also have hemal arches
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15
Q

Describe ribs in Necturus

A

Ribs are bicipital:
• The tuberculum attaches to the dorsal part of the transverse process (diapophysis).
• The capitulum attaches to the ventral part of the transverse process (parapophysis).

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16
Q

Vertebral column in Anurans

A

Regional variation in anuran vertebral column:
• Cervical vertebra* (1)
• Trunk vertebrae* (variable)
• Sacral vertebra* (1)
• Caudal vertebrae (1)
- Urostyle = single caudal vertebra in
anurans.
- Modified adaptation for saltatory
locomotion:
- Attachment site for muscles involved in
jumping.
• Ilia tie pelvic girdle into vertebral column
through sacral vertebra.
• Collectively comprise the precaudal vertebrae

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17
Q

Two pairs of zygapophyses in salamanders

A 
The cranial (anterior) zygapophyses have articular facets that face dorsally.
• The caudal (posterior) zygapophyses have articular facets that face ventrally
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18
Q

Describe amniote vertebra

A

Parts of an amniote vertebra are similar to those of the
Necturus vertebra.
- They consist of:
• Centrum
• Neural and hemal arches (with spines)
• Transverse processes
• zygapophyses

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19
Q

Describe amniote centrum

A

The centrum functionally replaces the
notochord.
• Classification of centrum based on shape of
cranial and caudal ends:
• Amphicoelous: both ends are concave
(Some reptiles)
• Procoelous: only cranial end is concave
(Most reptiles)
• Opisthocoelous: only caudal end is concave
• Acoelous: both ends are flat (Mammals)

20
Q

What can be found in tails

A

In the tails of reptiles and some mammals
small pieces of bone may be found between
the ventral edges of centra:
• Intercentra (or hypocentra)
• Form hemal arches (chevron bones)

21
Q

Describe pleura/intercentrum in amniotes

A
  • In primitive reptiles the bulk of the centrum
    is formed from the pleurocentrum.
  • In modern reptiles and mammals the intercentrum has disappeared and the centrum is formed entirely from the pleurocentrum
  • Intercentrum persists in Sphenodon
22
Q

Describe neural arch in amniotes

A

Neural arch consists of a neural spine and
diapophyses.
• Diapophyses are for rib attachment.

Neural arch is composed of lateral and dorsal plates which form the neural canal.
• Dorsal plates are the laminae and meet in the midline to fuse with the neural spine.
• Lateral plates are the pediceles which fuse to the centrum ventrally and to the laminae dorsally to form the transverse processes.
• The posterior edge of each pedicele is typically notched so that when vertebrae are articulated, holes are formed between them to allow the passage of spinal nerves.

23
Q

Describe development of vertebral column in amniotes

A 
The vertebral column develops from the
sclerotome portion of the embryonic somites.
• Somites are paired blocks of mesodermal tissue that form along the notochord during embryonic
development.
• Each somite consists of three major
components:
 • Dermatome:
     • Forms dermis of integument.
• Myotome:
     • Forms axial muscles.
• Sclerotome:
     • Forms parts of vertebrae.
24
Q

Describe sclerotomal breakup

A

• Sclerotomal portion of each
somite breaks up into an anterior and a posterior
portion.
• Posterior portion of one
somite joins the anterior portion of an adjacent
somite, etc.
• This creates gaps that allow
nerves to grow out from the neural tube into the epaxial segmental musculature derived from the myotomes.

25
Q

Regional variation in reptile vertebrae

A 
• Cervical vertebrae: (atlas-axis first appears in reptiles)
    • Atlas (#1):
          - Centrum becomes odontoid
process of axis.
    • Axis (#2)
    • 8 in most reptiles
    • 9 in alligator.
• Trunk:
    • Typically with ribs.
• Sacral vertebrae:
    • 2+
• Caudal vertebrae:
    • Variable with hemal arches.
26
Q

Regional variation in bird vertebrae

A
  • Cervical vertebrae:
    * With transverse foramina.
    * Hetereocoelous
    * 8-25
  • Anterior thoracic:
    * Wing brace.
  • Synsacrum:
    * Posterior thoracic.
    * Lumbar.
    * Sacral (2+)
    * Proximal caudal.
  • Pygostyle:
    * Fused caudal vertebrae
27
Q

Describe centrum in mammals

A 
• Generally acoelous
      • Except cervical vertebrae of ungulates
(opisthocoelous)
• Centrum derived from pleurocentrum
      • Intercentrum lost
28
Q

Describe atlas in mammals

A

• Articulates with two occipital condyles
• Lacks a centrum:
• Has become associated with C2
intercentrum as the odontoid process
(dens)
• Serves as axis for lateral rotation

29
Q

Describe cervical 3-7 in mammals

A

Possess short fused bicipital ribs that create
transverse foraminae:
• Pathway for vertebral arteries to brain

30
Q

Describe thoracic in mammals

A

Have articulation facets for ribs (costal facets)
• Costal facets on transverse processes
articulate with tubercles of ribs.
• Costal facets on centra articulate with
heads (capitula) of ribs.
• Most heads of ribs in upper part of
thoracic region articulate between two
adjacent centra, resulting in the
formation of costal demifacets.

31
Q

Describe lumbar vertebrae in mammals

A
  • Thicker centra

* No costal facets or ribs

32
Q

Describe sacral vertebrae in mammals

A

• Fused into a single element called the
synsacrum.
• Articular facets for pelvis

33
Q

Describe caudal vertebrae in mammals

A
  • Found in most mammals
  • May have indications of hemal arches
  • (chevron bones)
34
Q

Describe ribs in tetrapods

A 
• Arise in skeletogenous septa
• Dorsal ribs:
• Formed at intersections
between myosepta and
horizontal septum.
35
Q

Describe ribs in amphibians

A

Reduced

36
Q

Describe ribs in reptiles

A 
• Double-headed (bicipital):
    • Capitulum to centrum
    • Tubercle to transverse
process
• 8 pairs in turtle fused to carapace
37
Q

Describe ribs in birds

A

• Uncinate processes of one rib
overlap next caudal rib to
stabilize rib cage for flight.

38
Q

Describe ribs in mammals

A 
• Cervical ribs :
    • Short and fused to
vertebrae.
    • Transverse foramina for
vertebral arteries.
• Thoracic ribs :
    • Double-headed
    • True ribs articulate with
sternum via costal cartilages.
    • Floating ribs do not
articulate with sternum.
39
Q

Types of bones

A 
• Long bones:
    - Femur, tibia, humerus, phalanges
• Short bones:
    - Carpals and tarsals
• Flat bones:
    - Bones of skull cap, dermal bones)
• Irregular bones:
    - Vertebrae, facial bones
• Sesamoid bones:
    - Knee cap (patella)
40
Q

Bone markings

A 
• Depressions:
    - Foramen.
    - Groove (sulcus).
    - Fossa (-ae).
• Processes:
    - Spine.
    - Tuberosity.
    - Condyle.
    - Epicondyle.
41
Q

Describe joints

A

• Joint = an area where two bones meet.
• Articulation = where a movable joint is formed.
Classification is usually based on type of material
that holds the two bones together and the amount
of movement possible.

42
Q

Describe Ampiarthrosis

A 
Slightly movable joint
Joining material = cartilage
Synchondrosis type:
        - Joining material = hyaline cartilage
          Example: epiphyseal plate
Symphysis type:
       - Joining material = fibrocartilage.
         Example: pubic symphysis.
43
Q

Describe Synarthrosis

A 
Slightly movable joint
Joining material = fibrous connective tissue
    Suture type:
    - Example: joints between bones of skull cap
    Gomphosis type:
    - Example: tooth in socket.
    Syndesmosis type:
    - Example: interosseous membrane.
44
Q

Describe Diarthrosis

A 
Very movable joint.
Joining material = cartilage
Components:
Articular cartilage (AC)
Fibrous capsule (FC):
    - Innervated
Synovial membrane (SM):
    - Vascularized
Synovial cavity (SC)
45
Q

Joints: Movement and Degrees of Freedom

A 
Uniaxial:
• Movement in one plane around one axis:
• Example:
• Hinge joints (elbow, knee)
• Pivot joints (atlantoaxial)

Biaxial:
• Movement in two planes around two axes.
• Example:
• Ellipsoid (metacarpalphalangeal).

Triaxial:
• Movement in three planes around three axes:
• Example:
• Glenohumeral (shoulder)
• Acetabulofemoral (hip)

Nonaxial (sliding):
• No axis of rotation
• Example:
• Joints between carpals and tarsals

Comparative Anatomy 1 (9 decks)

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