Sectioning, Dissection and

Skeletal Elements

Sections

1-vertical sections 2-Transverse sections

V.S. of skin

1- Ascidia.2- Branchiostoma.

3- Petromyzon.4- Carchrinus.5- Chalcides.

T.S. of pharyngeal, trunk & tailregions.

1- L.S. of Ascidia.2- Branchiostoma.

3- Ammocoete larva.4- Carchrinus. 5- Oreochromis.6- Chalcides.

protochordates

vertebrates

protochordates

vertebrates

V.S. of skin

Epidermis

Single layer stratified

epidermis

epidermis

protochordates vertebrates

Epidermis consists of a single layer

Skin is covered with a thick testcontaining vascular ampullae Epidermis contains golblet cells

Ascidia Branchiostoma

test

epidermis

Goblet cell

epidermis

Stratified epidermis

Epidermis contains Club-shaped cells

Skin containsPlacoid scales

Skin is covered withhorny scales

PetromyzonCarcharinus Chalcides

Horny scalePlacoid scaleClub-shaped cell

sections

Notochord

absent Well developed Replaced by centra of vertebrae

L.S. ofAscidia

Consists ofMuscular plates

Branchiostoma

Consists ofVacuolated cells

Ammocoete larva

myotomes

ConcentricallyArranged muscle

lamellae

Carcharinus

Small muscle fibers

Skin Contains Cycloid scales

Skin is Covered withHorny scales

Oreochromis Chalcides

I-The notochord is entirely absent.

-The animal is surrounded with a thick test.

L.S. of Ascidia.

test

II- The notochord is well developed & surrouded by a fibrous sheath.

A-The notochord consists of muscular plates.

-The myosepta of one side alternate with those of the other side.

…….Sections in Branchiostoma….. (2)

myoseptum

notochord

Nerve cord

myotome

Fibrous

sheath

Muscle plates

B- The notochord consists of vacuolated cells and surrounded by a fibrous sheath.

- both myotomes and myosepta are dorso-ventrally directed.

……….Sections in ammocoete larva… (3).

Nerve cord

notochord

myotome

myoseptum

III-The large part of the notochord is replaced by centra of vertebrae.

……. Sections in Carcharinus, Oreochromis and Chalcides (A, B &C).

neural arch

nerve cord

centrum

Remnant of

notochord

Skeleton of pigeon

Skeletal system of rabbit

Cervical vertebrae

-Atlas & axis possess vertebrarterial foramens.

a-Atlas contains 2 condylar facets anteriorly &

two facets for axis posteriorly.

Vert. foramen

Facet for axis

Condylar

facet

b--Axis is characterized by

1-odontoid process anteriorly.

Odontoid process

2- postzygapophysis posteriorly.

postzygapophysis

The normal cervical vertebra is characterized by

1-anterior and posterior zygapophyses.

2-Vertebarterial foramen.

postzygapophysis

prezygapophysis

Vertebarterial

foramen

Neural spine

It is charaterized by:

1-long spine.

2-pre & postzygapophyses.

postzygapophysis

prezygapophysis

Lumbar is

characterized by:

1-long transverse

processes.

2-metapophyses.

3-Pre and

postzygapophyses.

Sacral vertebra is characterized by:

1-Broad transverse processes.

2-Pre and postzygapophyses.

Girdles

-with dorsal spine.

-with a glenoid cavity.

Dorsal spine

Glenoid

cavity

-With ilium and ischium bones.

- Contains acetabulum.

Dissection 1-Oreochromis:

2-Dissection of Chalcides

3-Dissection of rabbit