Embryology: Development of Speech and Hearing Systems

Question 1

Embryology

Answer 1

Human Embryology is the study of human development during the first 8 weeks

Question 2

Embryogenesis

Answer 2

The process of cell division and cellular differentiation of the human embryo that occurs during the early stages of development

Question 3

How does human development begin and occur?

Answer 3

Occurs along a continuum

Begins with germ cells (ovum and spermatozoon) and progressing to growth to adulthood

After the first 8 weeks, the embryo is then referred to as a fetus

Question 4

How many cells does a mature human body have?

Answer 4

10^14 cells

These cells will form and differentiate as the body grows

Some cells are replaced as they mature and die

Question 5

What is the first step in cell division?

Answer 5

Duplication of genes and chromosomes

Question 6

The process of development is characterized by?

Answer 6

The coordination of spatial and temporal changes in gene expression, cell growth or maturation, and cell differentiation

This process ultimately leads to the development of organs and systems

Question 7

Prenatal Development Means

Answer 7

Development that occurs during the first 8 weeks of gestation

Question 8

Prenatal Development - Week 2

Answer 8

The amniotic cavity develops, along with the primary germ or germinal layers of tissue:

Extoderm, mesoderm, and endoderm

These 3 layers of primary tissue ultimately give rise to all of the structures of the body

Question 9

Ectoderm

Answer 9

Outer most layer and forms the epidermis of the skin, much of the teeth, the entire nervous system (both PNS and CNS), hair nails, and epithelial tissue

Question 10

Mesoderm

Answer 10

The intermediate layer that ultimately gives rise to most of the connective tissue in the body.

In other words, it comprises the bones, muscles, blood vessels, and cartilages of the body

Question 11

endoderm

Answer 11

Deepest of the three layers. It gives rise to the epithelial lining of the entire digestive tract and respiratory tract

except for the linings of the oral and pharyngeal cavities, which are formed by ectoderm

Endoderm is sometimes referred to as “inner skin”

Question 11

Prenatal Development - 3rd week

Answer 11

The primitive streak appears, followed by rapid development of the CNS, heart, notochord, neural tube, limbs, digits, and facial features

Question 12

Primitive Streak is comprised of

Answer 12

number of cells that proliferate caudally

Significance of the primitive streak is that it is capable of forming new germ tissue (ectoderm, mesoderm, and endoderm)

Question 13

Notochord

Answer 13

Primitive axial (forming or relating to axis) skeleton of the embryo

Cephalically (of or related to the head), some tissues of the notochord will develop that will form the buccopharyngeal membrane

Question 14

At 3 weeks, the facial area is

Answer 14

Very primitive (early stage)

Consists of smooth, relatively undifferentiated bulge known as the PROSENCEPHALON, which is the forebrain or anterior brain of the embryo

Question 15

Caudal to the prosencephalon (forebrain) lies a?

Answer 15

Transverse furrow called the oral groove or stomodeum (primitive mouth)

Question 16

STOMODEUM means

Answer 16

primitive mouth and is regarded as the center of the developing facial structures

Question 17

At week 3, the ectoderm…

Answer 17

begins to thicken in an area immediately overlying the notochord

thickened layer of ectoderm is called the MEDULLARY or NEURAL PLATE - the lateral margins of which grow upward to form the NEURAL FOLDS

Eventually, the NEURAL FOLDS will meet at midline, fuse, and form the NEURAL TUBE

Question 18

Importance of the neural tube

Answer 18

Ultimately gives rise to the entire CNS, which comprises the brain and spinal cord

Question 19

3 subdivisions of neural tube

Answer 19

1. prosencephalon
2. mesencephalon
3. rhombencephalon

Question 20

Prosencephalon

Answer 20

Subdivision of neural tube

will further develop into the telencephalon (cerebrum) + diencephalon (optic vessels + hypothalamus)

Question 21

Mesencephalon

Answer 21

Subdivision of neural tube

Will eventually develop into mid brain

Question 22

Rhombencephalon

Answer 22

subdivision of neural tube

Will eventually develop into metencephalon (pons and cerebellum) and the myencephalon (medulla oblongata)

Question 23

The 4th and final subdivision of the neural tube will form the ?

Answer 23

Spinal cord

Neural tube is open both cranially and caudally before finally closing during the 4th week of development

Question 24

Openings in the neural tube called

Answer 24

Neuropores

Question 25

Failure of the neuropores to properly close may result in

Answer 25

neural tube defects

Example is spina bifida

Question 26

In the 4th week, what happens to the buccopharyngeal membrane

Answer 26

It ruptures, allowing the stomodeum (primitive mouth or oral cavity) to articulate with the pharynx

Question 27

4th week - migrating neural crest cells

Answer 27

These form the frontonasal process located in the anterior portion of the forebrain

A number of neural crest cells will form the branchial or pharyngeal arches

Together, the frontonasal process and branchial arches contribute greatly to the development of the FACE and ORAL CAVITY

Question 28

4-5 week of development Branchial and Pharyngeal arches are comprised of what

Answer 28

6 paired thickenings that form a LATERAL PLATE

Question 29

Mandibular Arch

Answer 29

First of the branchial arches

Gives rise to the lower lip, the muscles of mastication, and mandible proper, the anterior portion of the tongue, malleus and incus, tensor tympani, tensor veli palatini, mylohyoid, and the anterior belly of digastric

Question 30

Hyoid Arch

Answer 30

Second of the branchial arches

Gives rise to the upper body and lesser horns of the hyoid bone, the stapes, the muscles of facial expression, stapedius, stylohyoid, and the posterior belly of digastric

Question 31

Branchial arch 3

Answer 31

Gives rise to the lower body of the hyoid bone, the posterior portion of the tongue, and the stylopharyngeus

Question 32

Branchial Arch 4

Answer 32

Cartilages of the larynx, all muscles of the larynx and pharynx except stylopharyngeus, and all muscles of the soft palate (except tensor veli palatini)

Question 33

Branchial Arch 5 (mystery arch)

Answer 33

Some research suggests that it gives rise to the cricoid + arytenoid cartilages and the cartilages of the trachea

HOWEVER, more recent research has suggested that the 5th arch disappears during embryonic development and does not give rise to any structures or muscles in human embryo development

Question 34

Branchial Arch 6

Answer 34

Gives rise to the muscles sternocleidomastoid and trapezius

Question 35

All Branchial arches are innervated (supplied with nerves) by the CN

Answer 35

First: Trigeminal (V)

Second: Facial (VII)

Third: Glossopharyngeal (IX)

Fourth: Vagus (X)

Sixth: Accessory (XI)

Question 36

5th week: frontonasal process

Answer 36

Rapidly develops caudally

Gives rise to upper face, forehead, bridge o the nose, and nasal septum

Question 37

5th week - maxillary process

Answer 37

Develop and give rise to the maxilla

Question 38

5th week - mandibular process

Answer 38

Gives rise to the mandible

Question 39

6th week - maxillary and mandibular process can be distinguished from one another

T/F?

Answer 39

True

Towards the end of the 6th week of development, the hard and soft palates begin to develop

Question 40

7th week - soft palate + hard palate

Answer 40

soft palate forms through the fusion of the medial nasal processes

Hard palate forms through the fusion of the palatine processes of the maxillae + the horizontal lamina of the palatine bones

These fusions complete the formation of the ceiling of the oral cavity and the floor of the nasal cavity

Question 41

7-8 weeks - tongue formation

Answer 41

Tongue begins to form at about the same time as the hard and soft palates

It extends from various protuberances along the pharyngeal floor

It is derived from all pharyngeal arches contributing different components