Clock and Wavefront model
The model postulates the existence of a longitudinal positional information gradient down the AP axis of vertebrate embryos, which interacts with a smooth cellular oscillator (the clock), to set the time in each cell at which it will undergo a catastrophe.
What is the segmentation clock?
The vertebrate segmentation clock is a molecular oscillator that regulates the periodicity of somite formation. … Recent publications report the first identification of a molecular mechanism involved in the regulation of the pace of this oscillator.
What is the somite clock?
From Wikipedia, the free encyclopedia. The clock and wavefront model is a model used to describe the process of somitogenesis in vertebrates. Somitogenesis is the process by which somites, blocks of mesoderm that give rise to a variety of connective tissues, are formed.
How does Somitogenesis work?
Somitogenesis is the process by which somites form. Somites are bilaterally paired blocks of paraxial mesoderm that form along the anterior-posterior axis of the developing embryo in segmented animals. In vertebrates, somites give rise to skeletal muscle, cartilage, tendons, endothelium, and dermis.
What is the determination Front set by?
The determination front is manifest by the expression of a bHLH gene called Mesp2 (thylacine) in the anterior three somitomeres, marking future somite boundaries (Oginuma et al., 2008). … Genes downstream of FGF were activated with a distinct expression profile during somite segmentation.
How are somites formed?
Somite formation begins as paraxial mesoderm cells become organized into whorls of cells called somitomeres. The somitomeres become compacted and bound together by an epithelium, and eventually separate from the presomitic paraxial mesoderm to form individual somites.
Which part of each somite forms the muscles of the limbs and body wall?
The myotome is that part of a somite that forms the muscles of the animal. Each myotome divides into an epaxial part (epimere), at the back, and a hypaxial part (hypomere) at the front. The myoblasts from the hypaxial division form the muscles of the thoracic and anterior abdominal walls.
Which signaling pathway controls the periodicity of Somitogenesis?
The periodicity of somitogenesis is regulated by a molecular oscillator, the segmentation clock, driving cyclic gene expression in the unsegmented paraxial mesoderm, from which somites derive. Three signaling pathways underlie the molecular mechanism of the oscillator: Wnt, FGF, and Notch.
What is embryonic folding?
Embryonic folding converts a flat sheet of cells into a hollow, tube-like structure. Within the first 8 weeks of gestation, a developing embryo establishes the rudimentary structures of all of its organs and tissues from the ectoderm, mesoderm, and endoderm. This process is called organogenesis.
What is notochord in zoology?
notochord, flexible rodlike structure of mesodermal cells that is the principal longitudinal structural element of chordates and of the early embryo of vertebrates, in both of which it plays an organizational role in nervous system development. In later vertebrate development, it becomes part of the vertebral column.
What are embryonic somites?
somite, in embryology, one of a longitudinal series of blocklike segments into which the mesoderm, the middle layer of tissue, on either side of the embryonic spine becomes divided. Collectively, the somites constitute the vertebral plate.
What is primitive streak?
The primitive streak is a structure that forms in the blastula during the early stages of avian, reptilian and mammalian embryonic development. It forms on the dorsal (back) face of the developing embryo, toward the caudal or posterior end.
Are somites epithelial?
Somites bud off sequentially and rhythmically from the mesenchymal ‘paraxial’ mesoderm, arising as pairs of epithelial spheres that flank the neural tube and accumulate in a progressive A-P direction. … Together with cells from the midline notochord, the sclerotome differentiates into the vertebral column.
What is gastrulation biology?
Gastrulation is defined as an early developmental process in which an embryo transforms from a one-dimensional layer of epithelial cells (blastula) and reorganizes into a multilayered and multidimensional structure called the gastrula.
Which part of the Somite develops into the dermis on your calf?
V.
Somite gives rise to sclerotome, which develops into vertebral and rib bones; myotome, which develops into muscle, and dermatome, which develops into dermal connective tissue.
What causes the embryonic folding during human development?
Due to an increase in the length of the embryo, the cranial and caudal regions of the embryo move inferiorly. At the same time, the rapid growth of the neural tube and somites causes the lateral aspects of the embryo to fold inward.
Which of the following can each Somite differentiate into?
Somites are precursor populations of cells that give rise to important structures associated with the vertebrate body plan and will eventually differentiate into dermis, skeletal muscle, cartilage, tendons, and vertebrae.
What are the 4 stages of embryonic development?
- 1.1 Fertilization.
- 1.2 Cleavage.
- 1.3 Blastulation.
- 1.4 Implantation.
- 1.5 Embryonic disc.
How is an embryo produced?
From Egg to Embryo
First, the zygote becomes a solid ball of cells. Then it becomes a hollow ball of cells called a blastocyst. Inside the uterus, the blastocyst implants in the wall of the uterus, where it develops into an embryo attached to a placenta and surrounded by fluid-filled membranes.
What are the two types of embryonic folding?
- LONGITUDINAL FOLDING produces both head- and tailfolds, or flexion, and creates a cranial and caudal region to the embryo.
- TRANSVERSE FOLDING (FLEXION) produces right and left lateral folds.
Who are vertebrae?
Vertebrae are the 33 individual, interlocking bones that form the spinal column. Each vertebra has three main functional components: the vertebral body for load-bearing, the vertebral arch to protect the spinal cord, and transverse processes for ligament attachment.
Is spinal cord a notochord?
Notochord | Nerve cord |
---|---|
The notochord is a rod-like structure, which is formed from vacuolated cells. | The nerve cord is a chain of ganglia. |
Why Urochordates are called tunicates?
Urochordates are called tunicates because of the leathery covering or tunic. It provides protection.
What is neural crest?
The neural crest is a transient embryonic structure in vertebrates that gives rise to most of the peripheral nervous system (PNS) and to several non-neural cell types, including smooth muscle cells of the cardiovascular system, pigment cells in the skin, and craniofacial bones, cartilage, and connective tissue.
What is neural plate?
Definition of neural plate
: a thickened plate of ectoderm along the dorsal midline of the early vertebrate embryo that gives rise to the neural tube and neural crests.
What is mesenchyme tissue?
Mesenchyme is a type of animal tissue comprised of loose cells embedded in a mesh of proteins and fluid, called the extracellular matrix. … Mesenchyme directly gives rise to most of the body’s connective tissues, from bones and cartilage to the lymphatic and circulatory systems.
What is Trilaminar germ disc?
Anatomical terminology. A trilaminar embryo (or trilaminary blastoderm, or trilaminar germ disk) is an early stage in the development of triploblastic organisms, which include humans and many other animals. It is an embryo which exists as three different germ layers – the ectoderm, the mesoderm and the endoderm.
What is Hensen’s node?
Hensen’s node, also called the chordoneural hinge in the tail bud, is a group of cells that constitutes the organizer of the avian embryo and that expresses the gene HNF-3(&bgr;). During gastrulation and neurulation, it undergoes a rostral-to-caudal movement as the embryo elongates.
What is oropharyngeal membrane?
A transient ectodermal membrane formed in embryos where the anterior aspect of the primitive gut contacts the abdominal wall, separating the depression of the stomadeum from the primitive pharynx.
What are occipital Myotomes?
The occipital myotomes (4, light green) mainly form the pharynx (throat) and upper or anterior neck musculature, including the tongue muscles. They are also responsible for the musculature in the occipital head region.
Which gives rise to skeletal muscle?
The mesoderm gives rise to the skeletal muscles, smooth muscle, blood vessels, bone, cartilage, joints, connective tissue, endocrine glands, kidney cortex, heart muscle, urogenital organ, uterus, fallopian tube, testicles and blood cells from the spinal cord and lymphatic tissue (see Fig.
What is the process of Neurulation?
Neurulation is a process in which the neural plate bends up and later fuses to form the hollow tube that will eventually differentiate into the brain and the spinal cord of the central nervous system. From: Current Topics in Developmental Biology, 2012.