Embrology/ Developmental Of The Muscoloskeletal System

Front 1

_______or ______ usually occurs in the ampulla of the uterine tube when a sperm penetrates the ovum.

The nuclei of the two cells fuse to form a zygote or totipotent stem cell

Back 1

Conception or fertilization

Hint 1

Early development and formation of the three germ layers (pg.25)

Front 2

The nuclei of the two cells fuse to form a ________ or totipotent stem cell

Back 2

Zygote

Front 3

After fertilization, ________or cell division begins and forms a solid mass of dividing pluripotent stem cells, the morula, that travels down the uterine tube and reaches the uterine cavity at about 4 days after conception.

Back 3

Cleavage

Front 4

The solid morula becomes a hollow _________ that begins to implant into the endometrium of the uterus at about 6 days.

Back 4

Blastocyst

Front 5

During the second week of development, as implantation of the blastocyst continues, the cells that will become the embryo differentiate to form a bilaminar disc composed of an outer layer of cells, the ectodermal epiblast, and an inner layer of cells, the endodermal hypoblast.

Back 5

Bilaminar disc

Ectodermal epiblast

Endodermal hypoblast

Front 6

During the third week of development, after implantation is completed, the process of _________results in the formation of a third germ layer, the mesoderm and its

associated notochord.

Back 6

Gastrulation

Front 7

The primitive streak with the primitive node (pit) at its cephalic end appears in the caudal midline of the epiblast.

Back 7

Primate steak

Primitive note (pit)

Front 8

Cells of the epiblast invaginate into the primitive streak and node forming a new layer of cells lying between the epiblast and hypoblast. This intermediate or third layer of cells is the intraembryonic mesoderm.

Back 8

Mesoderm

Front 9

Cells invaginating into the primitive node migrate forward in the midline of the embryo and, after separating from the endoderm, form a narrow rod of cells, the notochord, which is the first part of the axial skeleton to appear.

Back 9

Notochord

Front 10

At the end of gastrulation, the embryo consists of three germ layers: an outer ectoderm, an inner endoderm and between them, the mesoderm. All of the tissues and organs of the adult are derived from these three germ layers.

Back 10

Outer ectoderm

Inner endoderm

Between the two above is the mesoderm

Front 11

What are the Ectodermal derivatives:

1) Central nervous system

2) Peripheral nervous system, including the medulla of the adrenal gland

3) Sensory epithelia of the ear, nose and eye

4) Epidermis, including the hair and nails

5) Epithelium of the cornea, conjunctiva and lacrimal glands

6) Lens

7) Smooth muscle of the iris

8) Epithelium lining the nose and paranasal sinuses, the roof of the mouth, the gums and

cheeks

9) Salivary glands and the enamel of the teeth

10) Mammary glands, pituitary gland and subcutaneous glands

Back 11

Ectoderm derivatives

Hint 11

Derivatives of the germ layers

Front 12

What are the Endodermal derivatives:

1) Epithelial lining of the digestive and respiratory tracts

2) Parenchyma of all the glands that open into the digestive tract, including the liver and pancreas, but excluding the salivary glands

3) Parenchyma of the thyroid and parathyroid glands, the thymus and tonsils

4) Epithelial lining of the urinary bladder, prostate and urethra

5) Epithelial lining of the auditory tube and tympanic cavity

Back 12

Endodermal derivatives

Front 13

What are the Mesodermal derivatives that include all the remaining tissues and organs of the body:

1) Connective tissue, cartilage and bone, dermis

2) Teeth, with the exception of the enamel

3) Striated and smooth muscles of the body, with the exception of the smooth muscle of the iris

4) Blood and lymph cells and the cardiovascular and lymphatic systems

5) Urogenital system, with the exception of most of the urinary bladder, prostate and urethra

6) Serous membranes lining the pericardial, pleural and peritoneal cavities

7) Cortex of the adrenal gland

Back 13

Mesodermal derivatives that include the rest of the remaining tissues and organs in the body

Front 14

What are the 3 regions of the mesoderm that will differentiate?

Back 14

The paraxial, intermediate, and lateral plate mesoderm

Hint 14

III. Differentiation of the mesoderm

Front 15

Around the 17th day some of the cells close to the midline proliferate and form the paraxial mesoderm.

The paraxial mesoderm will then further differentiate into somites.

Back 15

Form the paraxial mesoderm

Paraxial mesoderm turns onto sometimes

Front 16

The tissue next to the paraxial mesoderm (lateral to it) is called the_______.

The excretory units of the urinary system develop from this.

Back 16

intermediate mesoderm

Front 17

Laterally the mesoderm remains thin and is known as the lateral plate mesoderm.

It divides into two layers:

Back 17

Parietal mesoderm (somatic mesoderm)

Visceral mesoderm (splanchnic mesoderm)

Front 18

______will combine with overlying ectoderm to form the lateral and ventral body wall.

Back 18

Parietal mesoderm (somatic mesoderm)

Front 19

_________will combine with endoderm to form the wall of the gut tube, all layers of blood vessels, and heart tube.

Back 19

Visceral mesoderm (splanchnic mesoderm)

Front 20

What is the definition of a somite?

Back 20

precursor populations of cells on either side of the notochord that develop from the paraxial columns of mesoderm.

Hint 20

Formation of the somites

Front 21

The first pair of somites appears in the cervical region at about the 20th day. From here new somites arise in cranio-caudal sequence, approximately three per day, until at the end of the fifth week 42-44 pairs are present.

True or false

Back 21

True

Hint 21

Formation of the somites

Front 22

There are 4 occipital, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 8 to 10 coccygeal pairs. The first occipital and the last 5-7 coccygeal somites later disappear.

True or false

Back 22

True

Hint 22

Formation of the somites

Front 23

what does a Sclerotome form? The cells of the ventromedial part of the somite form the sclerotome.

During the fourth week the cells migrate medially to surround the spinal cord and notochord where they will form the vertebral column and ribs.

Back 23

Forms bones and cartilage

Hint 23

Differentiation of the somite

Front 24

These cells form a loosely woven tissue known as mesenchyme or young connective tissue. The mesenchymal stem cells differentiate into fibroblasts, chondroblasts and osteoblasts that synthesize and secrete the matrix of general connective tissue, cartilage and bone respectively.

Back 24

Mesenchyme

Hint 24

Differentiation of somite

Front 25

_______the portion of bones and joints supplied by a single dorsal root and its ganglion

Back 25

Sclerotome

Front 26

What do myotomes form?

Back 26

They form skeletal muscles

Front 27

After the sclerotome cells have migrated, the remaining cells of the somite give rise to a new layer of cells on its medial surface known as the myotome.

Back 27

Myotome

Front 28

At the end of the sixth week, the myotomes separate into a dorsal part, the epaxial muscles, and a ventral part, the hypaxial muscles.

• Epaxial muscles → intrinsic back muscles

• Hypaxial muscles → anterolateral muscles of the chest and abdominal wall, and limb musculature

Back 28

Myotome

Front 29

The cells of the myotome become elongated and spindle-shaped and are referred to as myoblasts or primitive muscle cells. The myoblasts fuse to form long multinucleate striated muscle fibers.

Back 29

Myoblasts

Front 30

myotome = the group of muscles supplied by a single ventral root.

Back 30

Myotome

Front 31

What does Dermatome contributes to the dermis of the skin?

Back 31

Dermatome

Front 32

After the myotome has formed, the remaining cells of the somite become the dermatome.

Back 32

Dermatome

Front 33

The dermatome cells form a mesenchyme that spreads out under the overlying ectoderm. Here they form the dermis and subcutaneous tissue of the skin.

Back 33

Dermatome

Front 34

Dermatome = a patch of skin whose sensory nerves all come from a single dorsal root and its ganglion

Back 34

Dermatome

Front 35

1.) Each somite forms its own sclerotome (the segmental connective tissue, cartilage and bone component), its own myotome (the segmental muscle component) and its own dermatome (the segmental skin component).

2.) There are as many sclerotomes, myotomes, and dermatomes as there are spinal segments (exception is C1; spinal nerve C1 lacks a significant afferent component and does not supply the skin, so no C1 dermatome).

3.) Therefore, each sclerotome, myotome and dermatome has its own segmental nerve component.

Back 35

Summary points taken away from page 30-31 for differentiation of somites.

Front 36

Somite derivatives and spinal nerve formation during the embryonic period (4-8 wks).

True or false

Back 36

True