SKULL AND VISCERAL SKELETON

• THE SKULL AND VISCERAL SKELETON

  SKULL

  ● neurocranium and its development.

  ● Dermatocranium and its origin.

  ● Basic structures of dermatocranium.

  ● Neurocranial-dermatocranial complexes of organisms.

  VISCERAL SKELETONS

  ● Splanchnocranium

  ● Differences among vertebrates in their visceral skeletons.
• NEUROCRANIUM

  ● Comprises of the upper and posterior areas of the skull. Serves as protection and support.

  DERMATOCRANIUM

  ● Made up of dermal bone, comprised of the outer layer of the skull’s roof and the facial skeleton.

  SPLANCHNOCRANIUM ● Comprised of upper and lower jaw. This develops within the pharyngeal arches, partially ossified.

  A) NEUROCRANIUM

  B) SPLANCHNOCRANIUM

  
• Neurocranium Development: Cartilaginous stage

  Cartilage that would form the plates:

  ● Parachordal cartilage - pair found parallel to the notochord's anterior end formed from the neural crest ectoderm. Will form the basal plate.

  ● Prechordal cartilage - pair found anterior to the parachordal cartilages formed from the lateral-plate mesoderm. Will form the ethmoid plate
• Neurocranium Development: Cartilaginous stage

  Sense Capsules:

  ● Olfactory - partially surrounds olfactory epithelium. Does not complete development to allow respiration.

  ● Optic - Partially surrounds the retina. Does not form the eye socket but rather the scleric coat. Does not completely unite with the skull for free movement.

  ● Otic - Surrounds the otocyst and develops the inner ear.

  A) OLFACTORY CAPSULE

  B) OLFACTORY SAC

  C) PRECHORDAL CARTILAGE

  D) PARACHORDAL CARTILAGE

  E) OPTIC CAPSULE

  F) OTIC CAPSULE

  
• Neurocranium Development: Cartilaginous stage

  • Floor - The ethmoid plate would then unite with the olfactory capsule, and the basal with the otic, before both plates unite and form a floor for the brain to rest.
  • Walls - Building of cartilaginous walls come after.
  • Roof - finally in forming a cartilaginous roof in the form of the tectum, with prominent fenestrae. fenestrae is typically a hole to connect the internal areas of the head to the outside, while the foramen are for inter-regional connection in the body
• Cartilaginous Neurocranium of Adult Vertebrates

  CYCLOSTOME

  ● The notochord is not connected to the basal plate.

  CARTILAGINOUS

  ● start in neurocranial development making the box like braincase or chondrocranium.

  LOWER BONY FISH

  ● the cartilaginous neurocranium is eventually partially or completely ossified.
• Neurocranium development: Ossification Centers

  OCCIPITAL

  ● situated at the back of the head. Centered at the foramen magnum.

  SPHENOID

  ● situated lateral to the midbrain and pituitary gland.

  ETHMOID ● in the immediate anterior of the sphenoid ossification center.

  OTIC ● situated in the areas of the otic capsules or the inner ear areas.

  A) ETHMOID

  B) OTIC

  
• Neurocranium development: Ossification Centers

  Neurocranium development: Ossification Centers

  A) ETHMOID

  B) SPHENOID

  
• HOW IT MAY HAVE FORMED?

  • The dermatocranium may have been derived from our dermal-plated ancestors. For instance, the large bony jaws of ancestral fish may have given rise to the smaller scales.
• BASIC STRUCTURES

  Roofing Bones

  ● Skull protection

  Marginal Bones - Precursor to bony vertebrate upper jaw. ● Premaxillae ● Maxillae Primary

  Palate Bones – roof of oral cavity.

  ● Palatine

  ● Parasphenoid

  ● Vomer

  ● Pterygoids and ectopterygoid

  Opercular Bones – protects and support gills.

  ● Opercular ● Subopercular ● Preopercular

  ● Interopercular
• NEUROCRANIAL-DERMATOCRANIAL COMPLEX OF BONY FISHES

  NEUROCRANIAL-DERMATOCRANIAL COMPLEX OF BONY FISHES

  
• NEUROCRANIAL-DERMATOCRANIAL COMPLEX OF MODERN TETRAPODS

  AMPHIBIANS

  PLATYBASIC

  ● Refers to the flat structure of the amphibian skull.

  COLUMELLA

  ● an ossicle in the middle ear area that conducts the soundwaves.

  
• NEUROCRANIAL-DERMATOCRANIAL COMPLEX OF MODERN TETRAPODS

  REPTILES

  Temporal fossae

  ● A cavernous opening in the temporal region of amniotes.

  Secondary Palates

  ● Divides the oral cavity into a nasal and oral passageway.

  
• NEUROCRANIAL-DERMATOCRANIAL COMPLEX OF MODERN TETRAPODS


  REPTILES:

  Cranial Kinesis

  ● or kinetism, is the movement of various parts of the skull independent of each other.
• NEUROCRANIAL-DERMATOCRANIAL COMPLEX OF MODERN TETRAPODS

  MAMMALS

  Sole bone of lower jaw

  ● The dentary makes up the sole bone of the mammalian lower jaw.

  Cranial Sinuses

  ● Function in helping with the weight of the head, respiration, and communication.

  Turbinal bones

  ● As opposed to most reptiles, mammals have three turbinal bones to help with respiration

  
• VISCERAL SKELETON

  • Meckel's Cartilage remnant of where the vertebrate mandible originated which acts as support for the jaw.
  • Function: tetrapod visceral skeletons have modifications to aid in their feeding habits, communication, and brachial respiration.
• VISCERAL SKELETONS NOTES:

  VISCERAL SKELETONS NOTES:

  A) CYCLOSTOME

  B) SHARKS

  C) BONY FISHES

  
• VISCERAL SKELETON NOTES

  VISCERAL SKELETON NOTES:

  
• PECTORAL AND PELVIC GIRDLE

  • They brace the appendages, providing stability and helping deal with pushback from water or substrate as the body moves.

  A) SUPRASCAPULA

  B) SCAPULA

  C) CORACOID

  D) POSTTEMPORAL

  E) SUPRACLEITHRUM

  F) CLEITHRUM

  G) POSTCLEITHRUM

  H) SCAPULACORACOID

  I) CLAVICLE

  J) SCAPULA

  K) CLEITHRUM

  L) POSTTEMPORAL

  M) SUPRACLEITHRUM

  N) POSTCLEITHRA

  O) CORACOID

  
• Major Components of the Pectoral Girdle:

  CLAVICLE:

  ● a curve interior bone that acts as a strut to support the shoulder.

  ● birds have furcula, or commonly known as the wishbone, which is consisted of two fused clavicle bones.

  ● in modern bony fishes (teleosts), the cleithrum is the major bone of the girdle.

  ● because of the rudimentary build of sea mammals, they do not have clavicles.

  
• CORACOIDS 


  CORACOIDS

  ● found in tetrapods and arose from an embryonic cartilaginous coracoid plate.

  ● one of the two endochondral bones of the pectoral girdle of tetrapods.

  ● strong bone that connects the cranial edge of the sternum to the shoulder joint complex.
• CLEITHRUM


  CLEITHRUM

  ● major bone of the pectoral girdle of bony fishes.

  ● J-shaped bone that provides surface area for muscular attachment.

  ● supports the scapula.

  ● joined by supracleithrum, surmounted by a post temporal element.

  
• TETRAPODS

  TETRAPODS:

  ● Interclavicle additional membrane bone in tetrapods after losing the post-temporal.

  ● Post-temporal braces the girdle against the skull in fishes.

  ● Guide:

  ● coracoid / procoracoid

  ● scapula

  ● scapular spine

  ▪ clavicle ▪ cleithrum ▪ in. interclavicle.
• Acromion Process

  • the origin of the acromial head of the deltoid muscle, which courses distally and covers the scapular neck.

  Mammalian Clavicle

  ● large in monotremes, insectivores, and primates

  ● in felines, the clavicle adapted and reduces into a splinter.

  ● eliminated in cetaceans, ungulates, and other mammals. ● absent in pigs, sheep, and cattle.

  A) SUPRASCAPULA

  B) SCAPULA

  C) CLAVICLE

  D) CORACOID

  E) XIPHISTERNUM

  F) STERNUM

  G) EPICORACOID

  H) EPISTERNUM

  I) OMOSTERNUM

  
• Osteichthyan pectoral girdles

  • Modifications of a basic morphologic pattern seen in early bony fishes
  • Consisting of three cartilages or endochondral bones
  • Consisting of four or five membrane bones derived from the dermal armory
• Endoskeletal components of pectoral girdle


  • Coracoids
  • Scapulae
  • Suprascapulae
• Coracoids are absent in therian mammals
• Scapula is universal except to species that do not have forelimbs
• Dermal bones of pectoral girdle

  • Clavicles
  • Cleithra
  • Supracleithra
  • Posttemporals
  • Postcleithra
• Only fishes have cleithra and supracleithra
• Modern bony fishes


  Tend to lose the replacement bones of the pectoral girdle
• Tetrapods

  Lose dermal bones of the pectoral girdle