Comparative vertebrate anatomy

Comparative vertebrate anatomyLecture I IntroductionComparative Vertebrate AnatomyComparative Vertebrate Anatomy is the study of vertebrate structure (or morphology) and the functional aspects of these structures.

It is a study of vertebrate morphology from an evolutionary perspective.

The Phylum ChordataThe phylum chordata is made up of a group of animals all possessing four common features.

NotochordDorsal Hollow Nerve CordPharyngeal SlitsPostnatal Tail

These features are:

a rigid cartilaginous rod defining the longitudinal axis in the embryo

Fate of notochord during development: Head region - incorporated into floor of skullTrunk & tail - surrounded by cartilaginous or bony vertebrate (except in Agnathans)

1. Notochord

Adults: Fishes & amphibians - notochord persists the length of the trunk & tail but is constricted within the centrum of each vertebraReptiles, birds, & mammals - notochord almost disappears during development (e.g., remains as a pulpy nucleus in the vertebrae of mammals)Protochordates - notochord remains as the chief axial skeletonAgnathans - lateral neural cartilages are located on notochord lateral to the spinal cord1. Notochord

1. The vertebrate nerve cord is dorsally oriented and hollow.a] It consists of the brain and spinal cord.b] The hollow center of the vertebrate nerve cord is termed the Neurocoel.1] The neurocoel includes the central canal of the spinal cord.

2. DORSAL HALLOW NERVE CHORD

2) The nerve cord originates by the process of Neuralation.a] Neuralation typically occurs along the longitudinal axis of the embryo dorsal to the notochord.1] A groove, termed the Neural Groove, will form dorsal to the notochord.a} The neural groove will sink into the embryonic body and close off to form the Neural Tube.2. DORSAL HALLOW NERVE CHORD

2) The nerve cord originates by the process of Neuralation.b] In Agnathans and Neopterygians (the gars, bowfins, and teleosts) neuralation has become slightly modified from the typical vertebratepattern.1] The neural groove does not form.2] Instead a Neural Keel forms. The neural keel is a wedge shaped ectodermal structure dorsal to the notochord.a} It will separate from the surface ectoderm, form a cavity,and become a typical nerve cord.2. DORSAL HALLOW NERVE CHORD

3) The nerve cord expands anteriorly to form the brain.

4) Cranial and spinal nerves will develop and radiate out from thenerve cord.a] These nerves allow for communication between the CNS and the rest of the body.2. DORSAL HALLOW NERVE CHORD

PharynxThe pharynx is a vital portion of the vertebrate embryo.

a] It shows the relationship between vertebrates and other chordates.b] It produces a number of structures:1] gills in fish2] lungs in tetrapods3] jaw skeleton and musculature4] some endocrine glands5] the middle ear in tetrapods

3. PHARYNGEAL SLITS

PharynxThe pharynx is a vital portion of the vertebrate embryo.

a] It shows the relationship between vertebrates and other chordates.b] It produces a number of structures:1] gills in fish2] lungs in tetrapods3] jaw skeleton and musculature4] some endocrine glands5] the middle ear in tetrapods6] and serves a source of stem immune cells in the human fetus.

3. PHARYNGEAL SLITS

PharynxThe pharynx is a vital portion of the vertebrate embryo.

c] As a result, all vertebrate embryos will show a basic pharyngeal architecture.3. PHARYNGEAL SLITS

region of alimentary canal exhibiting pharyngeal pouches in embryo; pouches may open to the exterior as slits:

permanent slits - adults that live in water & breathe via gillstemporary slits - adults live on land

3. PHARYNGEAL SLITS

region of alimentary canal exhibiting pharyngeal pouches in embryo; pouches may open to the exterior as slits:

a} In fishes pharyngeal slits are maintained throughout life for gills.

b} In tetrapods pharyngeal slits are only temporarystructures.3. PHARYNGEAL SLITS

b} In tetrapods pharyngeal slits are only temporarystructures.1} Examples:(a) Frogs have 6 pharyngeal pouches in theembryonic form.(1) Four will form the gill slits of the tadpole.[a] These four slits will close up again during the metamorphosis into the adult frog.

(b) Chick embryos will have six pouches. Pharyngeal pouches number 1, 2, and 3 will rupture and then close up again.3. PHARYNGEAL SLITS

b} In tetrapods pharyngeal slits are only temporarystructures.1} Examples:

(c) In mammals only one or two pharyngeal pouches will rupture. The rupturing pouches tend to beanterior pouches and will close up again.(1) Pharyngeal pouch number one becomes the Eustachian Tube.(2) Pharyngeal pouch number two will eventually house the palatine tonsils.(3) Several posterior pharyngeal pouches will giverise to certain endocrine glands.3. PHARYNGEAL SLITS

Provides propulsion for swimming4. Postanal Tail

REVIEW