In humans, the
mesoderm is one of the three primary germ cell layers - the other two are the
ectodermThe ectoderm is the start of a tissue that covers the body surfaces. It emerges first and forms from the outermost of the germ layers.Generally speaking, the ectoderm differentiates to form the nervous system, and the epidermis .In vertebrates, the ectoderm has three parts: external ectoderm , the ...
and endoderm - in the very early
embryoAn embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
. The
mesodermIn humans, the mesoderm is one of the three primary germ cell layers - the other two are the ectoderm and endoderm - in the very early embryo. The mesoderm is the middle layer. It differentiates to gives rise to a number of tissues and structures including bone, muscle, connective tissue, and the...
is the middle layer. It differentiates to gives rise to a number of tissues and structures including bone, muscle, connective tissue, and the middle layer of the skin. Some cells in mesodermal tissues retain the capacity to differentiate in diverse directions. For example, some cells in the bone marrow (mesoderm) can become liver (endoderm).
More generally, the mesoderm is one of the three
germ layerA germ layer is a group of cells, formed during animal embryogenesis. Germ layers are particularly pronounced in the vertebrates; however, all animals more complex than sponges produce two or three primary tissue layers...
s found in the
embryoAn embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
s of
animalAnimals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously...
s more complex than
cnidariaCnidaria is a phylum containing over 10,000 species of animals found exclusively in aquatic, mostly marine, environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey...
ns, making them triploblastic. Mesoderm forms in the
embryoAn embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
during
gastrulationGastrulation is a phase early in the development of most animal embryos, during which the morphology of the embryo is dramatically restructured by cell migration. Gastrulation varies in different phyla...
when some of the cells migrating inward to form the
endodermEndoderm, is one of the germ layers formed during animal embryogenesis. Cells migrating inward along the archenteron form the inner layer of the gastrula, which develops into the endoderm....
, produce an additional layer that lies between the endoderm and the
ectodermThe ectoderm is the start of a tissue that covers the body surfaces. It emerges first and forms from the outermost of the germ layers.Generally speaking, the ectoderm differentiates to form the nervous system, and the epidermis .In vertebrates, the ectoderm has three parts: external ectoderm , the ...
.
Mesoderm is found in all large, complex animals, and allows the formation of a
coelomBy the broadest definition, a body cavity is any fluid filled space in a multicellular organism. However, the term usually refers to the space, located between an animal’s outer covering and the outer lining of the gut cavity, where internal organs develop...
, which allows more room for independent growth of the body organs.
General
The body organs, tissues and systems derived from the mesoderm in most triploblastic animals can be listed as follows:
- bones
- cartilage
Cartilage is a stiff yet flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
- most of the circulatory system
- [Headline text]--75.137.171.242 01:21, 21 October 2009 :bThe circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, nitrogen waste products, etc. to and from cells in the body to help fight diseases and help stabilize body temperature and pHb to maintain...
, including the heartThe heart is a muscular organ found in all vertebrates that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
and major blood vessels
- connective tissue
Connective tissue is a form of fibrous tissue.. It is one of the four types of tissue in traditional classifications ....
s of the gut and integumentsThe integumentary system is the organ system that protects the body from damage, comprising the skin and its appendages...
- mesenchyme
Mesenchyme, or mesenchymal connective tissue, is an example of reticular connective tissue, a type of loose connective tissue, which is derived from all three germ layers and located within the embryo . Mesenchyme is characterized morphologically by a prominent ground substance matrix containing a...
- mesothelium
The mesothelium is a membrane that forms the lining of several body cavities: the pleura , peritoneum and pericardium . Mesothelial tissue also surrounds the male internal reproductive organs and covers the internal reproductive organs of women...
- muscles
The muscular system is the anatomical system of a species that allows it to move. The muscular system in vertebrates is controlled through the nervous system, although some muscles can be completely autonomous.- Muscles :...
- peritoneum
The peritoneum is the serous membrane that forms the lining of the abdominal cavity or the coelom — it covers most of the intra-abdominal organs — in higher vertebrates and some invertebrates...
(lining of the abdominal cavity)
- reproductive system
The reproductive system is a system of organs within an organism which work together for the purpose of reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes of differentiated...
- spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells, holds a reserve in case of hemorrhagic shock, especially in...
- urinary system
The urinary system is the organ system that produces, stores, and eliminates urine. In humans it includes two kidneys, two ureters, the bladder, the urethra, and the penis in males...
, including the kidneyThe kidneys are paired organs, which have the production of urine as their primary function. Kidneys are seen in many types of animals, including vertebrates and some invertebrates. They are part of the urinary system, but have several secondary functions concerned with homeostatic functions. ...
s
Vertebrates
Before formation of the items in the above list, the mesoderm of a developing vertebrate transitionally differentiates into the following sub-types:
- Chordamesoderm
Chordamesoderm, also known as axial mesoderm, is a type of mesoderm that lies along the central axis, under the neural tube.* will give rise to notochord* starts as the notochordal process, whose formation finishes at day 20....
(also known as axial mesoderm) which later on gives rise to notochord in all chordates
- Paraxial mesoderm
Paraxial mesoderm is the area of mesoderm that forms just lateral to the neural tube on both sides.It gives rise to the somitomeres/somites and mesoderm of the branchial arches.*Somites form the vertebral column, dermis and skeletal muscle...
- Intermediate mesoderm
Intermediate mesoderm is a type of mesoderm that is located between the paraxial mesoderm and the lateral plate.It develops into the part of the urogenital system * forms of urogenital system...
- Lateral plate mesoderm
Lateral plate mesoderm is a type of mesoderm that is found at the periphery of the embryo.-Division into layers:It will split into two layers, the somatic layer/mesoderm and the splanchnic layer/mesoderm* The somatic layer forms the future body wall....
See also
- Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
- Embryogenesis
Embryogenesis is the process by which the embryo is formed and develops. It starts with the fertilization of the ovum which, after fertilization, is referred to as a zygote. The zygote undergoes rapid mitotic divisions with no significant growth and cellular differentiation, leading to...
- Embryology
Embryology is the study of the development of an embryo. An embryo is defined as any organism in an early stage well before birth or hatching, or in plants, before germination occurs....
- Ectoderm
The ectoderm is the start of a tissue that covers the body surfaces. It emerges first and forms from the outermost of the germ layers.Generally speaking, the ectoderm differentiates to form the nervous system, and the epidermis .In vertebrates, the ectoderm has three parts: external ectoderm , the ...
- Endoderm
Endoderm, is one of the germ layers formed during animal embryogenesis. Cells migrating inward along the archenteron form the inner layer of the gastrula, which develops into the endoderm....
- Germ layer
A germ layer is a group of cells, formed during animal embryogenesis. Germ layers are particularly pronounced in the vertebrates; however, all animals more complex than sponges produce two or three primary tissue layers...
- Histogenesis
Histogenesis is the formation of different tissues from undifferentiated cells. These cells are constituents of three primary germ layers, the endoderm, mesoderm, and ectoderm...
- Organogenesis
In animal development, organogenesis is the process by which the ectoderm, endoderm, and mesoderm develop into the internal organs of the organism. Internal organs initiate development in humans within the 3rd to 8th weeks in utero...