Skeletal System - The Skull Flashcards by Miyaki Jan Lim

Skeletal framework of the head

Skull = cranium = head skeleton

How well did you know this?

Not at all

Perfectly

the skulll of vertebrates are composed of these

Main braincase, the cranium (neurocranium) which surrounds and protect the brain

Sense capsules associated in development with the olfactory, auditory and visual sense organs

Numerous components of the visceral skeleton

How well did you know this?

Not at all

Perfectly

the skull is composed of three originally independent units:

Neurocranium or primary braincase
Dermatocranium
Splanchnocranium or visceral skeleton

How well did you know this?

Not at all

Perfectly

part of the skeleton that is loosely associated in early vertebrates and closely associated in amniotes

skull

How well did you know this?

Not at all

Perfectly

Components of the Cranium
Cartilage or endochondral bone
Floor and wall of braincase and sense capsules

Neurocranium

How well did you know this?

Not at all

Perfectly

Components of the Cranium
Membrane or dermal bone but never cartilage nor endochondral bone
Superficial covering of the skull (roof and sides of skull and parts of the mandible)

Dermatocranium

How well did you know this?

Not at all

Perfectly

Components of the Cranium
Cartilage or endochondral bone
Part of the visceral skeleton (gill arches) associated with the skull
Mostly visceral arches I and II

Splanchnocranium

How well did you know this?

Not at all

Perfectly

Components of Splanchnocranium

composed of the embryonic upper jaw cartilage and its replacement bones
Embryonic lower cartilage and its replacement and investing bones

How well did you know this?

Not at all

Perfectly

Components of the Cranium

Protects the brain and certain special sense organs

Arises as cartilage

Subsequently partly or wholly replaced by bone except in cartilaginous fishes

Neurocranium

How well did you know this?

Not at all

Perfectly

how is the Neurocranium formed

Starts as several independent cartilages that later expand and unite to form a cartilaginous braincase

How well did you know this?

Not at all

Perfectly

Embryology process

After the formation of the embryonic brain, the mesenchyme differentiate to form a membranous layer called the membranous cranium

The notochord extends forward beneath the brain, terminating near the infundibulum

The membranous cranium surrounds the anterior portion of the notochord

The parachordal plates are located lateral to the notochord and otic capsules

Prechordal cartilages formed in front of the parachordals

How well did you know this?

Not at all

Perfectly

The ventral region of the membranous cranium will become the ______

neurocranium

How well did you know this?

Not at all

Perfectly

Neurocranium begins as pair of ______________ cartilages below the brain

parachordal and prechordal cartilages

How well did you know this?

Not at all

Perfectly

plates that are located lateral to the notochord and otic capsules

parachordal plates

How well did you know this?

Not at all

Perfectly

expand and join along with the notochord to form the basal plate enclosing the tip of the notochord and later becomes the floor beneath the midbrain and the hindbrain

Parachordal cartilages

How well did you know this?

Not at all

Perfectly

______________ formed in front of the parachordals

Prechordal cartilages

How well did you know this?

Not at all

Perfectly

cartilages expand and join to form an ethmoid plate that later will become the rostrum

Prechordal

How well did you know this?

Not at all

Perfectly

contributes to the formation of the internasal septum between the nasal capsules

rostrum

How well did you know this?

Not at all

Perfectly

Simultaneou with the formation of cartilages, three pair of capsules are formed from the developing sense organs:

Nasal capsules from the olfactory sense organ
Otic capsules from the auditory sense organ
Optic capsules from the optic sense organ

How well did you know this?

Not at all

Perfectly

fuses with olfactory capsules and the basal plate fuses with otic capsules to complete the roof, sides and floor of the brain

ethmoid plate

How well did you know this?

Not at all

Perfectly

unite posteriorly leaving a prominent opening in the center, the hypophyseal fenestra, where the pituitary gland lies

prechordals and parachordals

How well did you know this?

Not at all

Perfectly

Endochondral ossification occurs more or less simultaneously at 4 regional ossification centers:

Occipital
Sphenoid
Ethmoid
Otic

How well did you know this?

Not at all

Perfectly

Cartilage surrounding the foramen magnum can be replaced by as many as 4 bones:

Supraoccipital bone dorsally
Exoccipital bones laterally
Basioccipital bone ventrallly

How well did you know this?

Not at all

Perfectly

One or more of the 4 may remain cartilaginous in what modern class of vertebratesn

modern amphibians

How well did you know this?

Not at all

Perfectly

Cartilage surrounding the foramen magnum can be replaced by as many as 4 bones and All four bones fuse in mammals to form a single bone called the

occipital bone

Articulation of the neurocranium with the 1st vertebra is via the ________

occipital condyles

what class have a single condyle borne out of the basioccipital bone

Stem amphibians

two classes that have a single condyle

Living reptiles and birds

two classes that have shifted the condyle to the two exoccipitals

Modern amphibians and mammals

what centers Osssifies independently in the synapsid and reptilian lineages

Sphenoid Centers

sphenoid that forms from the cartilage underlying the midbrain and pituitary gland

Basisphenoid

sphenoid that ossifies anterior to the basisphenoid in mammals Also contributes to the sidewall above the basisphenoid

Presphenoid

sphenoid bone (crocodiles and dinosaurs) forms the lateral ossification of the sphenoid redion

Laterosphenoid

sphenoid bone (archosaurs) forms a separate interorbital septum

Orbitosphenoid

sphenoid bone helps to form the lateral wall in some mammals though it is derived from the palatoquadrate cartilage

Alisphenoid

Sphenoid Centers

Basisphenoid, presphenoid, alisphenoid, Laterosphenoid, Orbitosphenoid

mammals can form a single sphenoid bone with wings

Basisphenoid, presphenoid and alisphenoid

Lies anterior to the sphenoid and includes the _________ and olfactory capsules Tends to remain cartilaginous in tetrapods from amphibians to mammals

Ethmoid Centers

No replacement bones develop above the brain

true

Pituitary gland rests on the ________ of the basisphenoid regions

tella surcica

Most basal tetrapods develop no ____________ whatsoever

ethmoidal ossification centers

Ossification centers in amniotes are chiefly _____________

mesethmoid bones

Ossification centers in amniotes are chiefly mesethmoid bones contribute to:

Cartilaginous nasal septum of birds and mammals and the anterior portion of interorbital septum in birds One or more scroll-like turbinal bones (conchae) of most reptiles, birds and mammals Cribriform plate perforated by olfactory foramina in mammals

in anurans is the sole bone arising in the ethmoid and sphenoid regions

Sphenethmoid

develops in the lateral walls of the nasal passageway of Sphenodon

Ectethmoid

cartilages found in the nasal passages are not from ethmoid ossification

Winglike alar bone and small sesamoid cartilages

capsule surrounding the membranous labyrinth becomes the prootic, opisthotic and epiotic

Otic capsule

One or more may unite with adjacent replacement of mebrane bones

Otic Centers

fuse with exoccipitals in frogs and nonavian reptiles

Opisthotics

unite to form a single periotic or petrosal bone in mammals

Prootic, opisthotic and epiotics

may unite with the squamosal to form a temporal bone

Petrosal bone

Occipital bones in Fishes (Teleost) Amphibians Reptiles/Birds Mammals

Supraoccipital Exoccipital Basioccipital

Mesethmoid bone is present in what classes

Mammals (ethmoid) (absent in primitive mammals and ungulates) Fishes (Teleost)

Ethmoid region in Fishes (Teleost) Amphibians Reptiles/Birds Mammals is ossified, unossifed, or turbinals

Fishes (Teleost) - ossified Amphibians - unossifed Reptiles/Birds - unossifed Mammals - turbinals

are these sphenoid bones present in each class Sphenethmoid Orbitosphenoid Basisphenoid Pleurosphenoid

fish Sphenethmoid Orbitosphenoid Basisphenoid Pleurosphenoid ampibhians Sphenethmoid Orbitosphenoid Basisphenoid Aves, Reptiles Sphenethmoid Orbitosphenoid Basisphenoid Pleurosphenoid (crocodiles and amphibians) Mammals Sphenethmoid Orbitosphenoid Basisphenoid

Laterosphenoid is only present in what animal

snake

whatotic capsule perotic part is present in what classes

Fishes (teleost) Prootic Epiotic Sphenotic Amphibians Prootic Opisthotic Aves absent Reptiles Prootic Epiotic Sphenotic Mammals Petrosal withvmastoid process

This bone is of dermal origin, so it is not strictly homologous to tetrapod _________.

mesethmoid

This bone is usually absent or reduced in some fishes.

Basisphenoid

Associated with the filter-feeding surfaces Generally supports the gills and offer attachment for respiratory muscles Contributes to the jaws and hyoid apparatus of gnathostomes May remain cartilaginous or become covered by dermal bones

Splanchnocranium

Declines in importance in tetrapods but never disappears

Splanchnocranium

Each visceral arch consists of a:

Skeleton Branchiomeric muscle Cranial nerve Aortic arch Gill filaments

came from neural crest cells departed from the sides of the neural tube and migrate into the walls of the pharynx between successive pharyngeal slits Differentiate into respective pharyngeal arches

Blastemas

are associated with their respiratory gill system called branchial or gill arches in aquatic vertebrates

Pharyngeal arches

Each arch is composed of a series of up to five articulated elements on each side (from dorsal to ventral):

Pharyngobranchial Epibranchial Ceratobranchial Hypobranchial Basibranchial

The first fully functional arch of the jaw is the ____________, which is the largest and most cranial Composed of the dorsal palatoquadrate and ventral Meckel’s cartilage

mandibular arch

The arch that follows the mandibular arch composed of the myomandibula

hyoid arch

Mouth of agnathans is not supported by jaws The __________ supports the roof of the pharynx and lateral pharyngeal slits

splanchnocranium

agnathan fish that were restricted to a diet of small particulate food

Ostracoderms

adaptation in agnathans for eating food

In some groups, small teeth-like structures derived from the surface scales, surrounded the mouth and used to scrape rocks for food The mucus-lined walls of the pharynx collected these scraped food particles from the passing stream

Jaws first appeared in ____________ that used them as food traps or as crushing or chewing devices to process food in the mouth

acanthodians and placoderms

The branchial arches gave rise to jaws as proposed by two separate theories on its origin:

Serial theory Composite theory

what theory says that the jaws arise completely from one of the cranial branchial arches Elements may be lost within it, but other elements from other arches do not contribute

Serial Theory

the theory that imples that the mandibular arch is formed from elements of several adjacent arches that also contribute to the neurocranium The palatoquadrate forms from the fusion of the epibranchial of the premandibular arch with the epibranchial and pharyngobranchial of the mandibular arch Meckel’s cartilage arises from the enlarged ceratobranchial element Hyoid arch arises from the epibranchial, ceratobranchial and hypobranchial elements of the 3rd gill arch The other elements of the primitive arches are lost and fused to the neurocranium

Composite Theory

Types of Jaw Attachment

Paleostylic Euautostylic Amphistyly Hyostyly Metaautostyly Craniostyly

Characteristic of agnathans None of the arches attach directly to the skull

Paleostylic

Found in placoderms and acanthodians Mandibular arch is suspended from the skull by itself without the aid from the hyoid arch

Euautostylic

Found in early sharks, some osteichthyans and crossopterygians Attached to the braincase through two primary articulations Cranially by a ligament connecting the palatoquadrate to the skull Caudally by the hyomandibular

Amphistyly

Found in most bony fishes The mandibular arch is attached to the braincase primarily through the hyomandibula with the aid of the symplectic bone

Hyostyly

Found in most amphibians, reptiles and birds Attached to the braincase directly through the quadrate bone Formed in the caudal part of the palatoquadrate

Metaautostyly

Found in mammals The entire upper jaw is part of the braincase but the lower jaw called dentary bone is suspended from the dermal squamosal bone of the braincase The palatoquadrate and Meckel’s cartilages remain cartilaginous except at their posterior ends which becomes the incus and malleus of the middle ear respectively

Craniostyly

Earliest vertebrates are encased in bony dermal armor and the extent to which it covers the body is variable Bony plates are present in the head

Dermatocranium