Embryo Test 3

Front 1

Pharyngeal Apparatus

Back 1

During the 4th week of development, the most cephalic region of the embryo develops the pharyngeal apparatus.

Front 2

The first pharyngeal arch forms two prominences:
 

Back 2

maxillary and ventro mandibular

Front 3

pharyngeal arches develop

Back 3

brick of mesoderm invaded by a population of neural crest cells invade the future head and neck regions.

Front 4

By the end of the 4th week of development,

Back 4

four pairs of pharyngeal arches are visible (the fifth quickly regresses, 1-4 and 6 form - but 6 is not visible).

Front 5

cntributions of 4 parts of pharyngeal arches

Back 5

contribute extensively to the formation of the head and neck.

Front 6

Between the two parts of the first arch there develops a thin membrane

Back 6

the oropharyngeal membrane, this membrane has two layers: an outer layer of ectoderm and an inner layer of endodermthis membrane eventually ruptures and produces and opening from the pharynx to the amniotic cavity.

Front 7

Components of a pharyngeal arch

Back 7

each pharyngeal arch is lined externally by ectoderm and internally by endoderm
each arch also contains a core of mesenchyme (derived from mesoderm and neural crest; skeletal muscle and vascular endothelium are derived from mesodermal mesenchyme

Front 8

a typical pharyngeal arch contains the following:

Back 8

1.cartilagenous bar
2. artery
3. cranial nerve
4. muscle component

Front 9

First Arch - Trigeminal Nerve

Back 9

muscles of mastication
mylohyoid and anterior belly of the digastric
tensor tympani
tensor veli palatini

Front 10

Second Arch - Facial Nerv

Back 10

muscles of facial expression
stapedius
stylohyoid
posterior belly of the digastric

Front 11

Third Arch - Glossopharyngeal

Back 11

Stylopharyngeus

Front 12

Fourth and Sixth Arches - Vagus Nerve

Back 12

laryngeal muscles
cricothyroid from 4th arch (superior laryngeal nerve)
remaining from 6th arch (recurrent laryngeal nerve)
pharyngeal constrictors
levator veli palatini
skeletal muscle of the esophagus

Front 13

Pouches

Back 13

The inside of the developing pharynx exhibits a number of pouch-like projections.
These pouches involve the endodermal lining and project from the inside of the pharynx towards the outer ectodermal lining.
There form four pharyngeal pouches.
Each pouch is situated between the adjacent arches (i.e. the first pouch is between the first and second arch).

Front 14

Thyroid Gland

Back 14

the thyroid descends from the pharynx to the neck and remains connected to the tongue via a thyroglossal duct
the superior opening of the thyoglossal duct remains open as a small pit on the dorsum of the tongue (foramen cecum)
in about 50% of individuals there is a pyramidal lobe of the thyroid and is a remnant of the thyroglossal duct

Front 15

Neurocranium

Back 15

– around the brain

Front 16

Viscerocranium

Back 16

skeleton of the face

Front 17

The Skull
Cartilaginous Neurocranium (chondocranium)

Back 17

Prechordal cartilage: up front
Parachordal cartilage: in the
back
Hypophysial cartilage: in
The middle

Front 18

neurocranium capsules

Back 18

Olfactory capsule: up front
Otic capsule: most posterior;
Surrounds organ for hearing and
balance
Optic capsule: middle part; surround
Eyes, contribute to sphenoid

Front 19

Membranous Neurocranium
Flat bones of skull

Back 19

made by neural crest cells
** connected via fibrous connective tissue; “fontanelles”

Front 20

Five facial primodia form

Back 20

frontonasal prominence
2. two maxillary prominences – from first arch
3. two mandibular prominences – from first arch

Front 21

development of face

Back 21

Maxillary prominence begins to slide toward center
Medial nasal prominences fuse; forms relatively significant part of face
Medial nasal prominences fuse; forms relatively significant part of face
Medial nasal prominences fuse; forms relatively significant part of face
When medial nasal prominences fuse they form intermaxillary segment;
externally part of lip-> filtrum (indentation of upper lip)
contributes to maxillary bone-> pulls four incisors together
primary palate

Front 22

nasolacrimal duct

Back 22

drains tears from eyes to the nose; invagination from ectoderm, can be blocked

Front 23

Incisive foramen

Back 23

; landmark between primary and secondary palate

Front 24

Development of the Palate

Back 24

Closure of septum and nasal cavity

Front 25

Congenital Deafness

Back 25

abnormal development of the parts of the inner or middle ear

Front 26

Inner Ear – Otic Placode

Back 26

gives rise to the membranous labyrinth of the inner ear

”statoacoustic” ganglion – cells from the otic placode and neural crest form the vestibulocochlear ganglion

Front 27

Membranous Labyrinth

Back 27

Otic vesicle goes from plain sac to smaller sacs
Utrical forms rings-> centers for balance; vestibular receptors
sacuole-> forms tail like structure that coils-> cochlear duct; auditory receptors

Front 28

Detail of the Membranous Labyrinth

Back 28

mesenchyme around the membranous labyrinth forms cartilage
supported by perilymph, perilymphatic duct
derivative of otic vesicle; vesicle filled with fluid (endolymph)
Space surrounding vesicle derivatives also filled with fluid (perilymph

Front 29

Development of the
Organ of Corti

Back 29

cochlear duct

the mesenchyme around the cochlear duct differentiates into cartilage, the cartilage then undergoes vacuolization
scala vestibuli
scala tympani

spiral ligament  tethers the cochlear duct to the surrounding cartilage

modiolus
cochlear duct epithelium
tectorial membrane

Front 30

Middle Ear Ossicles

Back 30

malleus and incus derive from the first arch

stapes derives from the second arch

Associated Muscles:
Tensor tympani: associated with malleus
Stapedius : attaches to stapes bone

Front 31

Development of:

Middle Ear

Back 31

after birth the tympanic cavity also invades the mastoid process (mastoid air cells)

Front 32

tympanic membrane derived from

Back 32

ectoderm, endoderm, mesoderm

Front 33

The eye develops from four sources

Back 33

Neuroectoderm – retina, posterior layers of iris and optic nerve
Surface ectoderm – lens and corneal epithelium
Mesoderm – fibrous and vascular coats
Neural crest – choroid, sclera and corneal endothelium

Front 34

Development of the Eye

During the 4th week

Back 34

optic vesicles grow out of the forebrain and lens placodes form. The ends of the optic cup will from the retina. Note that the retina has two layers: an inner layer and an outer layer.

Front 35

development of the eye

Back 35

A deep fissure forms along the optic stalk – the optic fissure (blood vessels occupy this space – the hyaloid artery).
The outer layer becomes the pigmented layer; the inner layer forms the neural retina.

Front 36

ciliary body derives from

Back 36

choroid mesenchyme and the optic cup.

Front 37

iris is formed

Back 37

at the edge of the optic cup; the gap that remains here is the pupil. The CT is from neural crest and the muscles derive from optic cup ectoderm.

Front 38

lens is derived from

Back 38

surface ectoderm (lens vesicle). The cells of the posterior wall become elongated and make a rounded surface, and obliterating the cavity. Lens fibers are created at the equator

The hyaloid artery supplies the developing lens – the artery becomes obliterated and the lens becomes avascular.

Front 39

cornea is derived from

Back 39

Surface ectoderm
Mesoderm – CT
Neural crest – corneal endothelium

Front 40

mesenchyme that surrounds the optic cup

Back 40

forms a inner vascular layer (choroid) and an outer fibrous layer (sclera)

Front 41

conjunctival sac is formed

Back 41

in relation to the lens placode and is lined by surface ectoderm. The eyelids begin as two folds that grow toward each other and fuse. Orbicularis oculi is derived from mesenchyme of the second pharyngeal arch. The lacrimal glands develop as pouches from the conjunctival sac.

Front 42

The extrinsic eye muscles form from

Back 42

preotic somites and form in a specific sequence:

Lateral and superior rectus – levator palpebrae arises from a splitting of the superior rectus
Superior oblique
Medial rectus, inferior rectus and inferior oblique

Front 43

oculomotor nerve reaches the orbit

Back 43

beginning of the 5th week and innervates the superior rectus, levator palpebrae, medial rectus, inferior rectus and inferior oblique. The trochlear nerve and abducens nerve reach the orbit at the end of the 5th week.

Front 44

If the two layers of the retina fail to fuse

Back 44

there is congenital detachment of the retina. Retinal detachment can also occur following a blow to the eye.

Front 45

Cyclopia

Back 45

Results - fusion of the eye in the midline; defects involving midline (often not compatible with life), often accompanied by a proboscis

Cyclopia – a single eye
Synophthalmia – incomplete fusion of the eyes

Front 46

Persistent Pupillary Membrane

Back 46

The pupillary membrane normally covers the anterior surface of the lens and disappears during development

Front 47

Congenital Glaucoma

Back 47

Indicated by an increase in intraocular pressure caused by a defect in the draining system; related to rubella infection.