Pharyngeal arches, limbs, and skeleton (final)

Question 1

The skeleton of the head and pharynx is made up of the _________________ which is bone that support the brain and sensory organs (olfactory organs, eyes, and inner ears), and the __________________ which is the bones of the face and pharyngeal arches

Answer 1

neurocranium, viscerocranium

Question 2

There are 2 types of bone in the head: ______________ bone forms from a cartilaginous intermediate and ossifies through the process of endochondral ossification. The bones of the cranial bones are formed by endochondral ossification and are collectively called the chondrocranium. The other type of bone develops from an ossification directly in the mesenchyme through the process of intramembranous ossification; this type of bone is known as membrane or __________ bone. The facial skeleton and the skull vault are formed almost entirely of membrane bone

Answer 2

endochondral, dermal

Question 3

Many of the skeletal structures in the head are unusual in that they form from ____________________ rather than from mesoderm

Answer 3

neural crest cells

Question 4

In humans, 5 pairs of transient (prominent, will flatten out) pharyngeal arches (also called brachial arches) form on either side of the _____________________ starting on day 22. These arches are numbered 1-5 in craniocaudal sequence

Answer 4

pharyngeal foregut

Question 5

Each pharyngeal arch has an outer overing ectoderm, an inner lining of endoderm, and a core of mesenchyme derived from paraxial and lateral plate mesoderm and neural crest cell-derived mesenchyme . The pharyngeal arches are separated externally by ectodermal-lined pharyngeal clefts (also called ___________) and internally by endodermal lined pharyngeal ___________

Answer 5

grooves, pouches

Question 6

The original mesoderm of the pharyngeal arches gives rise to __________________________. The muscular components of each arch have their own cranial nerve, and wherever the muscle cells migrate, they carry their nerve component with them

Answer 6

the musculature of the face and neck

Question 7

The 1st pharyngeal arch consists of a dorsal portion- the _____________ process, which extends beneath the region of the eye, and a ventral portion- the ________________ process

Answer 7

maxillary, mandibular

Question 8

What cartilage is the 1st pharyngeal arch made of?

Answer 8

Meckel

Question 9

Musculature of the 1st pharyngeal arch includes the muscles of….

Answer 9

mastication

Question 10

The nerve supply to the muscles of the 1st arch is provided by the mandibular branch of the….

Answer 10

trigeminal nerve (CN V)

note: this is sensory innervation only, no motor innervation with CN V

Question 11

The cartilage of the 2nd arch (aka hyoid arch- reichert cartilage), gives rise to-

Answer 11

-stapes
-styloid process of the temporal bone
-stylohyoid ligament
-hyoid bone

mesenchyme of the arch also forms most of the external ear

Question 12

Muscles of the 2nd (hyoid) arch are the muscles of….

Answer 12

facial expression

Question 13

What CN supplies the 2nd pharyngeal arch?

Answer 13

CN VII (facial n.)

Question 14

The cartilage of the 3rd pharyngeal arch produces the lower part of the body and greater horn of the ________ bone. The musculature is limited by the ________________ muscles. The cranial nerve is the _______________________

Answer 14

hyoid, swallowing, glossopharyngeal n. (CN IX)

Question 15

Cartilaginous components of the 4th and 6th pharyngeal arches fuse to form the __________- thyroid, cricoid, arytenoid, corniculate, and cuneiform cartilages. The muscles of the 4th arch constrict the pharynx. The cranial nerve associated with the 4th and 6th arch is the ________________

Answer 15

larynx, vagus n. (CN X)

Question 16

The human embryo has ______ pairs of pharyngeal pouches

Answer 16

4

Question 17

What are the derivatives of the 1st pharyngeal pouch?

Answer 17

-tympanic (middle ear) cavity
-auditory (eustachian) tube

Question 18

What are the derivatives of the 2nd pharyngeal pouch?

Answer 18

palatine tonsils

Question 19

What are the derivatives of the 3rd pharyngeal pouch?

Answer 19

inferior parathyroid gland and the thymus

Question 20

What are the derivatives of the 4th pharyngeal pouch?

Answer 20

superior parathyroid gland and thyroid gland

Question 21

The limbs, including the shoulder and pelvic girdles, comprise the appendicular skeleton. Limb buds form with the activation of a group of mesenchymal cells in the __________________ mesoderm

Answer 21

somatic lateral

Question 22

What genes regulate patterning in the formation of the limbs?

Answer 22

homeobox (Hox) genes

Question 23

The upper limb are visible on day 24 as small bulges on the lateral body wall at above the level of ________. By the end of the 4th week, the upper limb buds have grown to form pronounced structures protruding from the body wall

Answer 23

C5-T1

Question 24

After the upper buds, the lower limb buds first appear 1-2 days later, forming at about the level of ______

Answer 24

L1-S1

Question 25

Limb ________________ takes place from the 4th-8th weeks with development of the lower limbs lagging slightly behind that of the upper limbs

Answer 25

morphogenesis

Question 26

Each limb bud consists of a mesenchymal core of mesoderm covered by an epithelial cap of ectoderm. Along the distal margin of the limb bud, the ectoderm thickens to form an apical ectodermal ridge (AER). This structure maintains outgrowth of the limb bud along the…

Answer 26

proximal-distal axis

Question 27

Initiation of limb development starts with continued proliferation of the ________________ mesoderm in the limb region of the lateral body wall

Answer 27

somatic lateral plate

Question 28

As each limb bud forms, the ectoderm along the distal tip of the bud is induced by the underlying somatic mesoderm to form a ridge-like thickening called the ______________. This structure forms at the dorsal-ventral boundary of the limb bud and plays an essential role in the outgrowth of the limb

Answer 28

apical ectodermal ridge (AER)

Question 29

The mesenchyme adjacent to the AER consists of undifferentiated rapidly proliferating cells, whereas the mesenchymal cells proximal to it differentiate into blood vessels and cartilage bone models. The distal ends of the limb buds flatten into….

Answer 29

hand plates and foot plates

Question 30

In 6 week embryos, the terminal portion of the limb buds becomes flattened to form the hand and foot plates. Fingers and toes are formed when __________ in the AER separates this ridge into 5 parts

Answer 30

apoptosis

Question 31

During the 7th week of gestation, the limbs rotate in opposite directions. The upper limbs rotate __________ through 90 degrees on their longitudinal axis; as a result, the future elbows come to point dorsally, and the extensor muscles lie on the lateral and posterior aspects of the limb. The lower limbs rotate __________ through almost 90 degrees; therefore, the future needs come to face ventrally, and the extensor muscles lie on the anterior aspect of the limb

Answer 31

laterally, medially

Question 32

What week do chondrification centers appear?

Answer 32

5th week (by the end of the 6th week, the entire limb skeleton is cartilaginous, mesenchyme turns to cartilage)

Question 33

Osteogenesis of long bones in the 7th week from primary ossification centers in the middle of the cartilaginous models of the long bones. Ossification centers are present in all long bones by the _______ week

Answer 33

12th week

note: this is endochondral ossification

Question 34

From the dermomyotome regions of the somites, myogenic precursor cells migrate into the limb buds and later differentiate into////

Answer 34

myoblasts

Question 35

What are the 2 main types of limb anomalies/defects?

Answer 35

-amelia (the absence of a limb or limbs)
-meromelia (the absence of part of a limb, which includes hemimelia or phocomelia)

Question 36

What is amelia?

Answer 36

absence of a limb or limbs

Question 37

What is meromelia?

Answer 37

absence of part of a limb
-hemimelia= something missing, like the fibula from leg
-phocomelia= incorrect location/length, like the hands attached to the body

Question 38

Suppression of limb bud development during the early part of the 4th week results in the absence of the limb- aka ___________

Answer 38

amelia

Question 39

Arrest of disturbance of differentiation or growth of a limb during the 5th week results in various types of….

Answer 39

meromelia

Question 40

What is the axial skeleton composed of?

Answer 40

-cranium (skull)
-vertebral column
-ribs
-sternum

Question 41

During the 4th week, cells in the ______________ surround the neural tube and vertebrae start to develop

Answer 41

sclerotomes

Question 42

Mesenchymal cells from the sclerotomes are found in 3 main areas:

Answer 42

1) around the notochord
2) surrounding the neural tube
3) in the body wall