Gastrulation

Question 1

What does Mesoderm form ( 3 types)

Answer 1

Paraxial mesoderm

Intermediate mesoderm

Lateral plate mesoderm

Question 2

Give the function of Mesoderm

Answer 2

The mesoderm forms mesenchyme, mesothelium, non-epithelial blood cells and coelomocytes. Mesothelium lines coeloms

. Mesoderm forms the muscles in a process known as myogenesis, septa and mesenteries ( and forms part of the gonads (the rest being the gametes).[1] Myogenesis is specifically a function of Mesenchyme.

Question 3

What does the intermediate mesoderm form

Answer 3

The intermediate mesoderm connects the paraxial mesoderm with the lateral plate and differentiates into urogenital structures and gonads

Nephrotomes cranially
Nephrogenic cord caudally
(devlop into the gonads, ducts, kidneys etc.

Question 4

What does paraxial mesoderm form?

Answer 4

forms simultaneously with the neural tube. The cells of this region give rise to somites, blocks of tissue running along both sides of the neural tube, which form muscle and the tissues of the back, including connective tissue and the dermis

Question 5

What do Somites form

Answer 5

In response to signals from the notochord, neural tube and surface ectoderm, the somites subdivide and differentiate to give rise to the embryonic structures of the dermomyotome, myotome and sclerotome.

Question 6

what are somitomeres?

Answer 6

The approximately 50 pairs of somitomeres in the human embryo, begin developing in the cranial (head) region, continuing in a caudal (tail) direction until the end of week four.

The first seven somitomeres give rise to the striated muscles of the face, jaws, and throat.[2]

Rest bud off and give rise to Somites

Question 7

What do Somites form?

Answer 7

Sclerotome – tendon, cartilage & bone component

Myotome– providing the segmental muscle component (muscles of back)

•Dermatome– segmental skin component (dermis & subcutaneous tissue of skin)
Nerve component

Question 8

What does mesenchymal sclerotome form?

Answer 8

The cervical mesenchymal sclerotome gives rise to the cervical vertebrae and annulus fibrosus part of intervertebral disk.

Question 9

What is Lateral plate mesoderm?

Answer 9

A layer continuous with mesoderm covering the amnion (somatic/parietal mesodermal layer)

A layer continuous with mesoderm covering the yolk sac (Splanchnic/visceral mesodermal layer

•Together these layers line a newly formed cavity the intraembryonic coelom

Question 10

What is the intraembryonic coelem?

Answer 10

This space will give rise to the thoracic and abdominal cavities.

During the third week of development, the lateral mesoderm splits into a dorsal somatic mesoderm (somatopleure) and a ventral splanchnic mesoderm (splanchnopleure). The resulting cavity between the somatopleure and splanchnopleure is called the intraembryonic coelom

Question 11

What is Splanchic mesoderm?

Answer 11

Splanchnic (visceral) mesoderm overlies the endoderm and is a layer continuous with mesoderm covering the yolk sac. Splanchnic mesoderm gives rise to the mesothelial covering of the visceral organs.

, forms the heart as well as the visceral layer of the serous pericardium and blood vessels.

contributes to the smooth muscle and connective tissues of the respiratory and digestive organs

Question 12

What is Somatic Mesoderm?

Answer 12

Somatic mesoderm is the outer layer formed after the split of the lateral plate mesoderm (along the splanchnic mesoderm). It associates with ectoderm and contributes to connective tissue of body wall and limbs.

gives rise to the bones, ligaments, blood vessels, and connective tissue of the limbs.

Question 13

What else does Lateral Plate Mesodem contribute to?

Answer 13

The LPM also contributes to the development of dermis, pulmonary system components (lungs, larynx, bronchi), urinary system (bladder and urethra, glomular capillaries of Bowman’s capsule), spleen, adipose tissue, viscerocranial components of the head (including cartilaginous structures of the face and neck, mouth, tongue, pharynx, nasal cavities and portions of the ears), blood, lymphatic system and various other tissues, including the diaphragm, epithelium and mesenteries.

Question 14

What does lateral playte mesoderm do in temrs of limbs?

Answer 14

Cells from the lateral plate mesoderm and the myotome migrate to the limb field and proliferate to create the limb bud. The lateral plate cells produce the cartilaginous and skeletal portions of the limb while the myotome cells produce the muscle components. The lateral plate mesodermal cells secrete a fibroblast growth factor (FGF7 and FGF10, presumably) to induce the overlying ectoderm to form an important organizing structure called the apical ectodermal ridge

Question 15

What is the septum transversum?

Answer 15

The septum transversum is a thick mass of cranial mesenchyme, formed in the embryo, that gives rise to parts of the thoracic diaphragm and the ventral mesentery of the foregut in the developed human being

Question 16

What is extra embryonic mesoderm?

Answer 16

form from the hypoblast

The extraembryonic mesoderm fills the space between the trophoblast and the amnion and the chorion.

After the primary yolk sac is displaced by the definitive yolk sac (12 dpc), large cavities form within the extraembryonic mesoderm, which becomes confluent and forms the extraembryonic coelom cavity, thereby effectively splitting the mesoderm into two layers: the extraembryonic mesoderm, lining the chorion and amnion, and the extraembryonic mesoderm, covering the yolk sac.

The extraembryonic mesoderm also contributes to the formation of lymph, endothelium and blood.

Question 17

What do dermatomes contribute to?

Answer 17

The dermatome is the dorsal portion of the paraxial mesoderm somite which gives rise to the skin (dermis). In the human embryo it arises in the third week of embryogenesis.[2] It is formed when a dermamyotome (the remaining part of the somite left when the sclerotome migrates), splits to form the dermatome and the myotome.[2] The dermatomes contribute to the skin, fat and connective tissue of the neck and of the trunk, though most of the skin is derived from lateral plate mesoderm.[2]

Question 18

What does ectoderm form?

Answer 18

Generally speaking, the ectoderm differentiates to form the nervous system (spine, peripheral nerves and brain),[3][4] tooth enamel and the epidermis (the outer part of integument). It also forms the lining of mouth, anus, nostrils, sweat glands, hair and nails.[4]

Question 19

What does endoderm form?

Answer 19

The endoderm consists at first of flattened cells, which subsequently become columnar. It forms the epithelial lining of multiple systems

The embryonic endoderm develops into the interior linings of two tubes in the body, the digestive and respiratory tube

the trachea, bronchi, and alveoli of the lungs

Question 20

when do the lungs form ?

Answer 20

At day 22, lung buds form, remaining ensheathed in a splanchnopleuric mesoderm

Question 21

What cavities form?

Answer 21

In the 4th week the coelom divides into pericardial, pleural and peritoneal cavities.[2]

First partition: is the septum transversum.
This will be translocated later into the diaphragm and ventral mesentery.

Divides the coelom into primitive pericardial and peritoneal cavities

Pleuropericardial folds appear on the lateral wall of primitive pericardial cavity, which will eventually cause a partition to form the pericardial and pleural cavities.

Communication between these partitions formed by the pericardioperitoneal canals. However, pleuroperitoneal membranes will grow to fuse with the septum transversum to close off these canal