Comparative Anatomy Chordate Body Plan

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Comparative AnatomyChordate Body Plan
Kardong Chapters 2 4 Part 3
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Pharynx (fair-inks) with slits

• Figure 3.1. Pharyngeal arches
• lateral view and
• (b) ventral cross section.

• Pharyngeal arches- associated with slits
• Anamniotes (lower vertebrates)- have gill slits
• Amniotes- have slits in embryo but gills never
  form
• Endodermal pouches- pharyngeal pouch that grows
  toward surface of animal give rise to glandular
  tissue
• Ectodermal groove- pharyngeal groove on outside
  that grows toward each pouch

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Embryonic Features
Figure 3.2. Embryo pharyngeal arches.
Figure 3.3. Embryo development at 1 month.
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(a)

• In tetrapods, 1st pharyngeal slit becomes
  auditory tube and middle ear cavity
• Aortic arches housed within pharyngeal arches

(b)
Figure 3.4. Early pharyngeal devel. of shark (a)
early stage (b) later stage .
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Figure 3.5. Fate of the pharyngeal arches.

• 1st (mandibular) arch- mandibular and maxillary
  portions
• 2nd (hyoid) arch
• Other arches are numerically named
• Most vertebrates have 6 pairs of arches

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Figure 3.6. Pharyngeal arches.

• Each pharyngeal arch contains a cartilage,
  artery, mesoderm component, and cranial nerve.

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General Body Plan

• Head
• Trunk
• Tail

Figure 3.7. Sagittal section of craniate embryo.
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Head

• Head
• Cephalization- development of sense organs
• Protective covering of dermal bone (not
  replacement bone) or cartilage

Figure 3.8. Head region (internal view).
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Trunk

• Somites- muscle masses beside notochord
  embryonic structures that give rise to muscle and
  bone
• Coelom- body cavity between gut and body wall,
  lined by peritoneum

Figure 3.10. Gut region.
Figure 3.9. Coelom.
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Trunk (cont.)

• Other visceral organ cavities
• Heart- pericardium
• Lungs- pleura
• Abdomen- peritoneum

Figure 3.11. Pericardium cavity.
Figure 3.12. Pericardium and pleural cavities.
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Tail

• From vent/anus to end of the body.
• Somites and notochord
• Innervations
• Dorsal and ventral aorta
• Food storage, defense, locomotion

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Pituitary Development
Figure 3.13.

• Stomodeal ectodermal plate pushes inward and
  forms pocket (Rathkes pouch) that leads to
  anterior lobe
• This invagination meets the dienchephalons
  infundibular process which forms the posterior
  lobe

Figure 3.14.
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Morphological Characteristics of Vertebrates

• Divided into two superclasses Pisces and
  Tetrapoda
• Demonstrate bilateral symmetry
• Distinguishing features of vertebrates
• Presence of notochord
• Pharynx with slits
• Dorsal tubular nervous system
• Developed vertebrae
• Post anal tail

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Notochord

• Most primitive endoskeletal structure
• Jawless fish- notochord long and enlarged
• Cartilagenous fish- notochord surrounded by
  cartilagenous vertebrae
• Bony fish and amphibians- notochord surrounded by
  larger vertebrae
• Amniotes- notochord almost lost

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Notochord (cont.)

• In mammals, between successive centrums are disks
• Within disks, the notochord is mostly replaced
  with pulpy nucleus

Figure 3.15. Vertebrae.
Figure 3.16. MRI scan of vertebrae.
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More Vertebrate Features

• Dorsal nervous system
• CNS- brain and spinal cord
• Anamniotes- 10 pairs of cranial nerves
• Amniotes- 12 pairs of cranial nerves
• Vertebral column
• Backbones
• Post anal tail

Figure 3.17. Vertebral column.
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Anatomical Symmetry and Planes
Figure 3.18. Anatomical terminology.
Figure 3.19. Anatomical terminology.
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Cranial Nerves

• Olfactory
• Optic
• Oculomotor
• Trochlear
• Trigeminal
• Abducens
• Facial
• Vestibulocochlear
• Glossopharyngeal
• Vagus
• Amniotes (2 more)
• Spinal Accessory
• Hypoglossal

Figure 3.20. Mammalian cranial nerves.