Anatomy 🫀

Question 1

what do neural crest cells share in?

(concerning the development of face)

Answer 1

Neural crest cells share in formation of bones of the face after migration to pharyngeal arches.

Question 2

Mention some results of embryonic folding

(regarding the upper aspect of the embryo)

Answer 2

• Formation of head fold.
• Buccopharyngeal membrane is buried at the bottom of
  stomodeum (primitive mouth, located between forebrain
  cranially and primitive heart caudally).
• In the region between stomodeum and primitive heart, 6 pairs of curved elevations appeared at 4th week to start development of face and neck.

Question 3

what are the elements of every pharyngeal arch?

Answer 3

Each pharyngeal arch has 3 elements:

• Ectodermal covering.
• Endodermal lining.
• Mesenchymal core (invaded by a cranial nerve and aortic arch).

Question 4

what is the number of pharyngeal grooves between the arches?

Answer 4

5 grooves are present between 6 arches internally (pharyngeal
pouches) and externally (pharyngeal clefts).

Question 5

what happens to the first pharyngeal arch?

Answer 5

1st arch divides into 2 prominences on both sides of stomodeum. (maxillary & mandibular)

Question 6

what happens to the 5th pharyngeal arch?

Answer 6

5th arch disappears.

Question 7

what are the derivatives of pharyngeal clefts?

Answer 7

Question 8

what are the derivatives of pharyngeal pouches?

Answer 8

Question 9

what is the time of develoment of the face?

Answer 9

between the 4th and 8th weeks.

Question 10

what participates in the development of the face?

Answer 10

• Formation of the five facial processes around the stomodeum:

1. The frontonasal process: a median prominence, cranially (It arises from head fold).
2. Two maxillary prominences: one on each side (Dorsal part of first pharyngeal arch).
3. Two mandibular prominences: caudally (Ventral part of first pharyngeal arch).

Question 11

what are the developmental changes of the frontonasal process? (in development of face)

Answer 11

• The nasal placodes (An oval thickening of the surface ectoderm), develops on each side of the frontonasal process.
• Each nasal placode becomes invaginated to form a nasal pit with medial and lateral nasal folds.

Question 12

what are the developmental changes of the maxillary processes? (in development of face)

Answer 12

Each proliferates, grows medially pushing the medial nasal folds towards the midline to form intermaxillary segment.

Question 13

what are the developmental changes of the mandibular processes? (in development of face)

Answer 13

• They fuse with the maxillary process to form the cheek region.
• They fuse with each other medially to form the lower lip and chin.

“the upper lip consists of 3 parts, the lower lip consist of only 2”

Question 14

process of fusion of the maxillary processes and the lateral nasal folds

Answer 14

• The maxillary processes grow towards the lateral nasal folds and are separated from them by the nasolacrimal grooves.
• Later, ectoderm at floor of the nasolacrimal groove proliferates to form nasolacrimal duct.
• Its upper end dilates to form the lacrimal sac.
• The maxillary process fuses with the lateral nasal fold for continuity of the side.

Side note: maxillary prominences fuse with:

mandibular prominences: to narrow the stomodeum
medial nasal folds: to complete the formation of upper lip
lateral nasal folds: to form nasolacrimal duct

Question 15

process of fusion of the maxillary processes and the medial nasal folds

Answer 15

• The two maxillary processes grow in a medial direction and fuse with the two medial nasal folds to form the upper lip (formed of a central philtrum and two lateral parts).

Question 16

what are the derivatives of the intermaxillary segment?

Answer 16

❖ Labial component: Philtrum of upper lip.

❖ Jaw component: Part of the maxilla that bears the upper 4 incisors.

❖ Palatal component: Region of hard palate just posterior to the upper 4 incisors.

❖ Nasal septum.

Question 17

what forms the muscles of the face? and what innervates them?

Answer 17

• The face, cheeks and lips are invaded by mesenchyme of the second pharyngeal arch.
• This mesenchyme will give rise to the muscle of the face, which will be innervated by the facial nerve

Question 18

what is the time of development of the palate? and what are its parts?

Answer 18

6th week, primary & secondary

Question 19

where does the primary palate arise from?

Answer 19

the intermaxillary segment.

Question 20

what represents the primary palate

Answer 20

The primary palate is represented by the anterior triangular part of the hard palate.

Question 21

process of development of the secondary palate

Answer 21

1. Two shelf-like projections arise from the deep aspects of the maxillary prominences called palatal shelves.
2. Finally, they ascend to attain horizontal position above the tongue.
   - Medially: the shelves approach each other and fuse together in the median plane.
   - Anteriorly: they fused with the margins of the primary palate in a V-shaped manner.
   - Superiorly: they fuse with the nasal septum.

Question 22

what are the congenital anomalies of the face and palate?

Answer 22

1. Oblique facial cleft
2. Cleft upper lip
3. Cleft palate
4. Microstomia
5. Macrostomia
6. Dermoid cyst

Question 23

what are the features of oblique facial cleft?

Answer 23

It extends along the side of the nose to reach the medial angle of the eye.

Question 24

what is the cause of oblique facial cleft?

Answer 24

It results from failure of fusion between the maxillary process & the lateral nasal fold.

Question 25

what are the types and causes of cleft upper lip?

Answer 25

***- Unilateral cleft lip:*** It is due to failure of fusion between the **maxillary prominence & the medial nasal** process on **one** side only. ***- Bilateral cleft lip:*** It is due to failure of fusion between the **maxillary prominence & the medial nasal process** on **both** sides. ***- Median cleft lip:*** A **rare** abnormality is caused by **incomplete merging of the two medial nasal prominences** in the midline (i.e. the philtrum is absent).

Question 26

what characterizes median cleft lip?

Answer 26

Infants with midline clefts are often mentally retarded and have brain abnormalities

Question 27

what is the cause of cleft palate?

Answer 27

It is due to failure of fusion between the different segments of the palate

Question 28

what are the types of cleft palate?

Answer 28

- Diagram A: represents normal fusion of the lip and palate. - Diagram B: represents a unilateral cleft lip. - Diagram C: represents a unilateral cleft lip and alveolus. - Diagram D: represents a bilateral cleft lip and alveolus. - Diagram E: represents an incomplete (partial) cleft of secondary palate. - Diagram F: represents a unilateral complete cleft lip and palate.

Question 29

what is microstomia? and what causes it?

Answer 29

- Small oral orifice. - Due to excessive fusion between mandibular and maxillary processes.

Question 30

what is macrostomia and what causes it?

Answer 30

- Wide oral orifice. - Due to defective fusion between mandibular and maxillary processes.

Question 31

what are dermoid cysts?

Answer 31

Skin-lined cysts along line of fusion of face.

Question 32

what is the time of development of the pituitary gland **(Hypophysis Cerebri)**?

Answer 32

4th week.

Question 33

what is the origin of the pituitary gland?

Answer 33

Two ectodermal sources

Question 34

process of development of Adenohypophysis

Answer 34

1. **Upgrowth** diverticulum from roof of stomodeum **(Rathke’s pouch)**. 2. It grows towards the infundibulum forming a vesicle that is connected to roof of stomodeum by stalk. 3. The stalk disappears at 2nd month. 4. Vesicle differentiates into: - Anterior wall: Pars distalis - Posterior wall: Pars intermedia - Pars tuberalis: Wraps around the infundibulum. 5. The cavity forms cleft.

Question 35

Process of development of Neurohypophysis

Answer 35

**Downgrowth diverticulum from floor of diencephalon.** - Upper end: remains patent forming the infundibular recess of the 3rd ventricle. - Upper part: forms pituitary stalk. - Lower part expands to form pars nervosa.

Question 36

what are the anomalies of the pituitary gland?

Answer 36

1. Aplasia or hypoplasia of the pituitary gland 2. Pharyngeal pituitary gland

Question 37

what is **(aplasia / hypoplasia)** of the pituitary gland?

Answer 37

The pituitary gland is ill-developed and hypofunction due to **non or abnormal development Rathke's pouch**.

Question 38

what is **(pharyngeal pituitary gland)**?

Answer 38

**Accessory masses** of the anterior lobe tissue develop in the **roof of the oropharynx along remnant of the Rathke's pouch.**

Question 39

Development of thyroid gland

Answer 39

- Solid bilobed **endodermal** mass appears **at the site of foramen caecum** in adult tongue at **4th week** - It descends **anterior to hyoid bone then thyroid cartilage** till it reaches its **final position at 7th week** - It become formed of isthmus & 2 lobes - It remain connected to tongue by **thyro-glossal duct** - Para-follicular cells form 5th pharyngeal arch ## Footnote **(thyroid gland has 3 lobes) —-> two main + one from thyro-glossal duct**

Question 40

what is the fate of thyro-glossal duct?

Answer 40

**1. Proximal part:** above hyoid bone degenerate **2. Distal part:** forms pyramidal lobe & levator glandulae thyrodie

Question 41

movement of thyroid gland

Answer 41

Gland **move up / down with swallowing** due to: - Levator glandulae thyrodie connect pyramidal lobe with hyoid bone - Pre-tracheal Fascia fix the gland to thyroid, cricoid cartilage

Question 42

extension of thyroid gland

Answer 42

- Oblique line of thyroid cartilage to 5th tracheal ring - 5th cervical vertebra to 1st thoracic vertebra

Question 43

what is the arterial supply of the thyroid gland?

Answer 43

- Thyroida ima artery - Superior Thyroid artery - inferior Thyroid artery

Question 44

compare between superior & inferior thyroid arteries according to: origin Association Ligation Supply

Answer 44

Question 45

venous drainage of thyroid gland

Answer 45

- **Superior & middle thyroid:** drain into Internal jugular vein - **Inferior Thyroid:** drain into brachiocephalic vein

Question 46

lymphatic drainage of thyroid gland

Answer 46

**- Upper part:** drain into Upper deep Cervical LN **- Lower part:** drain into Lower deep Cervical LN **- Isthmus:** drain into Pre-tracheal LN

Question 47

what are the relations of the isthmus of thyroid gland?

Answer 47

**Anterior surface**: related to Sterno-hyoid & Sterno- thyroid **Posterior surface**: related to Tracheal ring (2,3,4) **Superior border**: related to Anastomosis between superior Thyroid arteries **Inferior border**: (related to) 1. Anastomosis between inferior Thyroid arteries 2. Inferior thyroid vein 3. Thyroida ima artery

Question 48

what are the relations of the lobes of thyroid gland?

Answer 48

**Lateral surface**: related to Sternomastoid, ,Sterno-hyoid, Sterno-thyroid & Superior Belly of omohyoid **Medial surface**: **(4 tubes)** 1. Upper part: related to Larynx, Pharynx& External Laryngeal nerve 2. Lower part: related to Trachea, Esophagus & Recurrent laryngeal nerve **Posterior surface**: related to Carotid sheath with its content

Question 49

development of parathyroid glands

Answer 49

- Superior parathyroid gland develop from 4th pharyngeal pouch - Inferior parathyroid gland develop from 3rd pharyngeal pouch

Question 50

what is the site of parathyroid glands?

Answer 50

On posterior border of thyroid gland

Question 51

what is the arterial supply of the parathyroid glands?

Answer 51

Inferior thyroid artery

Question 52

what is the nerve supply of the parathyroid glands

Answer 52

Superior & middle cervical sympathetic ganglion

Question 53

what are the derivatives of pancreatic buds?

Answer 53

Question 54

what is the origin of pancreatic ducts?

Answer 54

Question 55

what are the anomalies of development of pancreas?

Answer 55