Comparative AnatomyComparative Anatomy

Chordate Body PlanChordate Body Plan

KardongKardongChapters 2 & 4Chapters 2 & 4

Part 3 Part 3

"Numerous studies have demonstrated that students retain little of our

lectures, and research on determining the “average attention span,” while

varying, seems to congregate around eight to ten minutes (“Attention Span

Statistics,” 2015), (Richardson, 2010). " 

Pharynx Pharynx (fair-inks)(fair-inks) with slits with slits

Pharyngeal archesPharyngeal arches- associated with slits- associated with slits Anamniotes (lower vertebrates)- have gill slitsAnamniotes (lower vertebrates)- have gill slits Amniotes- have slits in embryo but gills Amniotes- have slits in embryo but gills nevernever form form

Endodermal pouchesEndodermal pouches- pharyngeal pouch that grows - pharyngeal pouch that grows toward surface of animal; give rise to glandular tissuetoward surface of animal; give rise to glandular tissue

Ectodermal grooveEctodermal groove- pharyngeal groove on outside that - pharyngeal groove on outside that grows toward each pouchgrows toward each pouch

Figure 3.1. Pharyngeal arches

(a) lateral view and (b) ventral cross section.

Embryonic FeaturesEmbryonic Features

Figure 3.2. Embryo pharyngeal arches.Figure 3.3. Embryo development at 1 month.

In tetrapods, 1In tetrapods, 1stst pharyngeal slit pharyngeal slit becomes auditory becomes auditory tube and middle ear tube and middle ear cavitycavity

Aortic arches housed Aortic arches housed within pharyngeal within pharyngeal archesarches

Figure 3.4. Early pharyngeal devel. of shark (a) early stage (b) later stage .

(a)

(b)

11stst (mandibular) arch- mandibular and maxillary (mandibular) arch- mandibular and maxillary portionsportions

22ndnd (hyoid) arch (hyoid) arch Other arches are numerically namedOther arches are numerically named Most vertebrates have 6 pairs of archesMost vertebrates have 6 pairs of arches

Figure 3.5. Fate of the pharyngeal arches.

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

Figure 3.6. Pharyngeal arches.

General Body PlanGeneral Body Plan

HeadHead TrunkTrunk TailTail

Figure 3.7. Sagittal section of craniate embryo.

HeadHead

HeadHead CephalizationCephalization- -

development of sense development of sense organsorgans

Protective covering of Protective covering of dermal bone (not dermal bone (not replacement bone) or replacement bone) or cartilagecartilage

Figure 3.8. Head region (internal view).

TrunkTrunk Somites- muscle masses Somites- muscle masses

beside notochord; beside notochord; embryonic structures that embryonic structures that give rise to muscle and give rise to muscle and bonebone

Coelom- body cavity Coelom- body cavity between gut and body wall, between gut and body wall, lined by peritoneumlined by peritoneum

Figure 3.9. Coelom.

Figure 3.10. Gut region.

Trunk Trunk (cont.)(cont.)

Other visceral organ Other visceral organ cavities:cavities: Heart- pericardiumHeart- pericardium Lungs- pleuraLungs- pleura Abdomen- peritoneumAbdomen- peritoneum

Figure 3.11. Pericardium & cavity.

Figure 3.12. Pericardium and pleural cavities.

TailTail

From vent/anus to end of the body. From vent/anus to end of the body. Somites and notochordSomites and notochord InnervationsInnervations Dorsal and ventral aortaDorsal and ventral aorta Food storage, defense, locomotionFood storage, defense, locomotion

Pituitary DevelopmentPituitary Development

Stomodeal ectodermal plate Stomodeal ectodermal plate pushes inward and forms pocket pushes inward and forms pocket (Rathke’s pouch) that leads to (Rathke’s pouch) that leads to anterior lobeanterior lobe

This invagination meets the This invagination meets the dienchephalon’s infundibular dienchephalon’s infundibular process which forms the process which forms the posterior lobeposterior lobe

Figure 3.13.

Figure 3.14.

Morphological Characteristics of Morphological Characteristics of VertebratesVertebrates

Divided into two superclasses: Pisces and Divided into two superclasses: Pisces and TetrapodaTetrapoda

Demonstrate bilateral symmetryDemonstrate bilateral symmetry Distinguishing features of vertebrates:Distinguishing features of vertebrates:

Presence of notochordPresence of notochord Pharynx with slitsPharynx with slits Dorsal tubular nervous systemDorsal tubular nervous system Developed vertebraeDeveloped vertebrae Post anal tailPost anal tail

NotochordNotochord

Most primitive endoskeletal structureMost primitive endoskeletal structure Jawless fish- notochord long and enlargedJawless fish- notochord long and enlarged Cartilagenous fish- notochord surrounded by Cartilagenous fish- notochord surrounded by

cartilagenous vertebraecartilagenous vertebrae Bony fish and amphibians- notochord surrounded Bony fish and amphibians- notochord surrounded

by larger vertebraeby larger vertebrae Amniotes- notochord almost lostAmniotes- notochord almost lost

Notochord Notochord (cont.)(cont.)

In mammals, In mammals, between successive between successive centrums are diskscentrums are disks

Within disks, the Within disks, the notochord is mostly notochord is mostly replaced with pulpy replaced with pulpy nucleusnucleus

Figure 3.15. Vertebrae.

Figure 3.16. MRI scan of vertebrae.

More Vertebrate FeaturesMore Vertebrate Features

Dorsal nervous systemDorsal nervous system CNS- brain and spinal cordCNS- brain and spinal cord Anamniotes- 10 pairs of cranial nervesAnamniotes- 10 pairs of cranial nerves Amniotes- 12 pairs of cranial nervesAmniotes- 12 pairs of cranial nerves

Vertebral columnVertebral column BackboneBackboness

Post anal tailPost anal tail

Figure 3.17. Vertebral column.

Anatomical Symmetry and PlanesAnatomical Symmetry and Planes

Figure 3.18. Anatomical terminology.

Figure 3.19. Anatomical terminology.

Cranial NervesCranial Nerves OlfactoryOlfactory OpticOptic OculomotorOculomotor TrochlearTrochlear TrigeminalTrigeminal AbducensAbducens FacialFacial VestibulocochlearVestibulocochlear GlossopharyngealGlossopharyngeal VagusVagusAmniotes (2 more)Amniotes (2 more):: Spinal AccessorySpinal Accessory HypoglossalHypoglossal

Figure 3.20. Mammalian cranial nerves.