Development of the Face Palate and Tongue Flashcards
Define growth
An anatomical phenomenon which involves an increase in size or number
Define development
A physiological phenomenon which involves an increase in organization, complexity or specialization
How many autosomes and sex chromosomes in the human somatic cell
44 autosomes
2 sex chromosomes (X and Y)
Describe fertilisation to the formation of the Morula
Sperm fuses with Oocyte to form the zygote.
Fertilised ovum undergoes cleavage.
The cells formed here are called blastomeres that rearrange themselves to differentiate into various groups and layers
4th day the zygote forms the many celled mass called a Morula.
What is a blastocoele and what does it do
As cell mass (morula) divides its enlarges and gains a fluid filled cavity = blastocoele (5th day)
Blastocoele separates cell into outer cell layer - trophoblast
inner cell mass - embryoblast
What does a blastocyst consist of
Inner cell mass - embryoblast
Outer cell layer - trophoblast
Blastocyst cavity - blastocoele
What does the embryoblast (inner cell mass) give rise to
the primitive endoderm and the epiblast
What do the primitive endoderm and epiblast develop into
Primitive endoderm - amniotic sac which forms the fluid filled cavity that the embryo resides in during pregnancy
Epiblast - develops into 3 germ layers of the developing embryo during gastrulation (endoderm, mesoderm and ectoderm)
What does the trophoblast do
Outer layer of the embryo that combines with maternal endometrium to form the placenta. also secretes factors to make the blastocoele
What is the cytotrophoblast
Cytotrophoblast is the inner layer of the trophoblast, composed of stem cells which give rise to cells comprising the chorionic villi, placenta.
What is the syncytiotrophoblast
Syncytiootrophoblast is the outermost layer of the trophoblast. These cells secrete proteolyGc enzymes to breakdown the endometrial extracellular matrix to allow for implantaGon of the blastocyst in the uterine wall.
What is implantation and when does it happen
Day 6
• The trophoblast attaches to the sticky endometrial surface on the posterior wall of the body of the uterus.
• The surface cells of the trophoblast produces enzymes that digest the uterine endometrial cells, which allows a deeper penetration of the cell mass.
In the second week what do the cells of the inner cell mass of the blastocyst differentiate into
Columnar shaped ectodermal cells and cuboidal shaped endodermal cells adjacent to the blastocoele. The amniotic cavity appears between the ectodermal cells and the overlying trophoblast
What is gastrulation and when does it occur
this is the conversion of the bilaminar to the trilaminar disc (ecto, meso, endoderm) in the third week of development
How is the trilaminar disc formed
Primitive streak forms and epiblast cells migrate through this streak towards the hypoblast, this eventually creates the three germ layers.
What do the ectodermal cells give rise to
the nervous system epidermis and appendages (hair, nails and sweat glands) enamel of teeth epthelium lining of the oral cavity. nasal cavities and sinuses
What do the endodermal cells give rise to
epithelial lining of the gastrointestinal tract and all associated organs
What does the mesoderm give rise to
the muscles and all the structures derived from the connective tissue (e.g., bone, cartilage, blood, dentin, pulp, cementum and the periodontal ligament).
What do the neural folds form into
The neural tube and the cells of the neural crest
What are the properties of the neural crest cells and what do they give rise to
multipotent
gives rise to ectodermal tissues and mesenchyme in specific areas of the head/face
What does the anterior end of the neural tube expand to form the beginnings of
The fore, mid and hindbrain
What occurs in the 4th week and is critical to the formation of the primitive oral cavity
Development of a head fold
What is the name for the primitive oral cavity
The stomatodeum
What separates the stomatodeum from the developing gut
the buccopharyngeal membrane
What are rhombomeres
The 8 bulges forming the hindbrain
The development of what forms the stomatodeum
A frontal prominence
What is the 1st branchial arch
The mandibular arch
What do the arches separate the stomatodeum from
the developing heart
What is found within each arch
Its own developing artery, cartilage and nerve.
What are the branchial arches
Structures that develop into the head and neck
What are the linings and core of the branchial arch made of
ectoderm - externally
endoderm - lined interally
neural crest derived mesenchyme core
What are the 4 elements of the branchial arch
Branchial arch
Branchial groove
Branchial pouch
Branchial membrane
What is the branchial groove
This is an ectodermal cleft between adjacent arches
What is the branchial pouch
endodermal out pocketing from rostral foregut?, between adjacent arches
What is the branchial membrane
This is the site of contact of the groove and pouch
What does the first branchial arch form
The face and have maxillary and mandibular processes surrounding stomodeum
What is the palatoglossal arch the site of
Site of the oropharyngeal membrane and boundary between oral cavity and pharynx.
How many arches are there
6
Which arch doesn’t form structures in humans
arch 5
What cranial nerves are the muscles of each arch innervated by
First arch - Trigeminal (V) Second Arch - Facial (VII) Third Arch - Glossopharyngeal (IX) Fourth arch - Vagus (X) Caudal Sixth - Accessory (XI)
What are the only branchial grooves and membranes that form structures in adults and what are the structures
the first groove - external auditory meatus (EAM)
The first membrane - tympanic membrane
What skeletal elements does each arch make
1st maxilla - Lateral wall of orbit, zygomatic bone, maxilla.
1st mandibular - Meckels cartilage
2nd hyoid - styloid process lesser horns of hyoid and connecting stylohyoid ligament
3rd - Greater horns of lower part of hyoid
4th - Thyroid, cricoid cartilages
6th - Arytenoids
What muscle groups do each arch make
1st maxilla - tensor veli palatini
1st mandibular - muscles of mastication and tensor tympani
2nd hyoid - muscles of facial expression
3rd - stylopharyngess
4th - constrictors of the pharynx, cricothyroid
6th - Intrinsic muscles of the larynx, striated muscle of the oesophagus
What are the 5 primordia that develop the face in the 4th week and what do they each form
Frontonasal Prominence - forehead and bridge of nose
2 Maxillary prominences - cheeks and upper jaw
2 Mandibular prominences - lower jaw and chin
What forms the philtrum of the upper lip
Maxillary prominences grow and fuse with the inter maxillary process
How can a bifid nose occur
if the medial nasal prominences don’t fuse together
What does the 6th week nasal pit do to the frontonasal prominence
Divides it into the lateral and medial nasal processes
How does the primary palate form
– forms from an internal swelling of the intermaxillary/premaxillary process (fusion of medial nasal processes)
How does the secondary palate form
Palatine shelves grow down on either side of tongue from maxillary prominences
• At same time, nasal septum grows down from base of the skull.
What do the palatine shelves do as the tongue descends into the throat
they rotate upwards and fuse in the midline and also fuse with the nasal septum
how does cleft lip form
Cleft lip is due to failure of maxillary prominences (palatine shelves) to fuse with intermaxillary process.
