Derivatives of the Pharyngeal Apparatus
The First Pharyngeal Arch |
Arch derivatives |
Muscle |
Mastication muscles (temporal, masseter, medial and lateral pterygoids), mylohyoid, anterior belly of the digastric, tensor velli palatini, tensor tympany |
Bone and cartilage |
Mandible, maxilla, premaxilla, zygomatic bone, squamous part of the temporal bone, pinna of the ear (anterior), Meckel's cartilage (malleus, incus) |
Other connective tissue |
Anterior ligament of the malleus, sphenomandibular ligament |
Pouch derivatives |
Middle ear cavity, auditory (Eustachian) tube, tympanic membrane |
Cleft derivatives |
External auditory meatus |
Nerve supply |
V (trigeminal nerve) |
The Second Pharyngeal Arch |
Arch derivatives |
Muscle |
Facial expresion muscles, stapedius, stylohyoid, posterior belly of the digastric |
Bone and cartilage |
Reichert's cartilage (stapes, styloid process), hyoid bone (leser horn and upper body), pina of the ear (posterior) |
Other connective tissue |
Stylohyoid ligament |
Pouch derivatives |
Palatine tonsils |
Cleft derivatives |
None |
Nerve supply |
VII (facial nerve) |
The Third Pharyngeal Arch |
Arch derivatives |
Muscle |
Stylopharyngeus |
Bone and cartilage |
Hyoid bone (greater horn and lower part of the body) |
Other connective tissue |
None |
Pouch derivatives |
Inferior parathyroid, thymus |
Cleft derivatives |
None |
Nerve supply |
IX (glossopharyngeal nerve) |
IV - VI Pharyngeal Arch |
Arch derivatives |
Muscle |
Cricothyroid, levator velum palatini, constrictors of pharynx, intrinsic muscles of the larynx |
Bone and cartilage |
Laryngeal cartilages (cricoid, thyroid, arytenoid, corniculate, cuneiforme) |
Other connective tissue |
None |
Pouch derivatives |
Superior parathyroid, ultimobranchial bodies of the thyroid |
Cleft derivatives |
None |
Nerve supply |
X (superior and recurrent laryngeal branch of the vagus nerve) |
Criteria for Estimating the Fertilization Age During the Fetal Period
Age (weeks) |
CR Length (mm) |
Weight (gm) |
Appearance of the fetus |
9 |
50 |
8 |
Eyes closed |
10 |
61 |
14 |
Intenstines in the abdomen |
12 |
87 |
45 |
Sex distinguishable externally |
14 |
120 |
110 |
Head erect |
16 |
140 |
200 |
External ears formed |
18 |
160 |
320 |
Vernix caseosa covers the skin
Fetal movements felt by the mother |
20 |
190 |
460 |
Lanugo hair visible |
22 |
210 |
630 |
Wrinkled skin |
24 |
230 |
820 |
Fingernails |
26 |
250 |
1000 |
Eyes partially open |
28 |
270 |
1300 |
Eyes wide open |
30 |
280 |
1700 |
Toenails present |
32 |
300 |
2100 |
Fingernails reach finger tips |
36 |
340 |
2900 |
Toenails reach toe tips |
38 |
360 |
3400 |
Prominent chest |
|
