During the 4th week of gestation, limb buds form on the sides of the developing embryo Embryo The entity of a developing mammal, generally from the cleavage of a zygote to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the fetus. Fertilization and First Week. The tips TIPS A type of surgical portasystemic shunt to reduce portal hypertension with associated complications of esophageal varices and ascites. It is performed percutaneously through the jugular vein and involves the creation of an intrahepatic shunt between the hepatic vein and portal vein. The channel is maintained by a metallic stent. The procedure can be performed in patients who have failed sclerotherapy and is an additional option to the surgical techniques of portocaval, mesocaval, and splenorenal shunts. It takes one to three hours to perform. Cirrhosis of these buds condense into the apical ectodermal ridge (AER). The AER continues the elongation Elongation Polymerase Chain Reaction (PCR) of the limb buds and maintains its growth by continuously producing fibroblast growth factor 8 Fibroblast growth factor 8 A fibroblast growth factor that preferentially activates fibroblast growth factor receptor 4. It was initially identified as an androgen-induced growth factor and plays a role in regulating growth of human breast neoplasms and prostatic neoplasms. Gastrulation and Neurulation (FGF8). As the AER grows away from the body, tissues differentiate. After the cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage: Histology models are formed in the developing limbs, arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology invade central and peripheral areas, giving rise to primary and secondary centers of ossification Ossification The process of bone formation. Histogenesis of bone including ossification. Bones: Development and Ossification. The process of endochondral ossification Ossification The process of bone formation. Histogenesis of bone including ossification. Bones: Development and Ossification is completed when those centers meet and the epiphyseal plate Epiphyseal plate The area between the epiphysis and the diaphysis within which bone growth occurs. Cartilage: Histology is no longer present.
Last updated: 11 Apr, 2022
Apical ectodermal ridge:
This ridge is located at the tip of the limb bud. Its function is the production of
fibroblast growth factor
Fibroblast growth factor
A family of small polypeptide growth factors that share several common features including a strong affinity for heparin, and a central barrel-shaped core region of 140 amino acids that is highly homologous between family members. Although originally studied as proteins that stimulate the growth of fibroblasts this distinction is no longer a requirement for membership in the fibroblast growth factor family.
X-linked Hypophosphatemic Rickets, which induces proliferation of ectodermal cells to maintain limb
elongation
Elongation
Polymerase Chain Reaction (PCR).
Mnemonic:
To quickly recall what happens during the 4th week, remember: 4 weeks → 4 limbs, 4 heart chambers
Rotation
Rotation
Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point.
X-rays of the limbs:
As upper and lower limbs grow, they bend at the elbow and knee with the palms and soles of the feet facing medially. During 90-degree opposite
rotation
Rotation
Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point.
X-rays, the elbow points toward the posterior side, whereas the knee points anteriorly.
Muscle comes from myotome: ventrolateral cells originating from somites located on either side of neural tube Neural tube A tube of ectodermal tissue in an embryo that will give rise to the central nervous system, including the spinal cord and the brain. Lumen within the neural tube is called neural canal which gives rise to the central canal of the spinal cord and the ventricles of the brain. Gastrulation and Neurulation that migrate to form muscles. As myotomes migrate, they form:
Myotome:
The myotome splits into a dorsal region, the epimere, that becomes the intrinsic muscles of the back, and a ventral region, the hypomere, that will become the muscles of the body wall and limbs.Hypomere:
As the hypomere migrates into the limb buds, it splits into dorsal and ventral muscle masses that will become extensors and flexors, respectively.
Musculature of the upper limbs
Somites corresponding to C4–C8, T1–T2 give rise to posterior and anterior aspects of the musculature of the upper limb. Flexor muscles arise from anterior aspects of these somites, while extensors arise from the dorsal aspects.
Cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage: Histology is developed from undifferentiated mesenchymal tissue and develops into the bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types by a process called endochondral ossification Ossification The process of bone formation. Histogenesis of bone including ossification. Bones: Development and Ossification.
Image by Lecturio.Primary center of ossification Ossification The process of bone formation. Histogenesis of bone including ossification. Bones: Development and Ossification is created by arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology invading the middle of the cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage: Histology. Bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types formation proceeds outward from it, as the blood also delivers osteoprogenitor cells.
Image by Lecturio.Secondary ossification Ossification The process of bone formation. Histogenesis of bone including ossification. Bones: Development and Ossification center is created by arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology invading the bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types extremities. The 2 centers of ossification Ossification The process of bone formation. Histogenesis of bone including ossification. Bones: Development and Ossification are separated by the epiphyseal plate Epiphyseal plate The area between the epiphysis and the diaphysis within which bone growth occurs. Cartilage: Histology.
Image by Lecturio.
Connective tissue
Connective tissue
Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix.
Connective Tissue: Histology:
As the bones grow,
connective tissue
Connective tissue
Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix.
Connective Tissue: Histology remains between them as dense
regular
Regular
Insulin
connective tissue
Connective tissue
Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix.
Connective Tissue: Histology or
fibrocartilage
Fibrocartilage
A type of cartilage whose matrix contains large bundles of collagen type I. Fibrocartilage is typically found in the intervertebral disk; pubic symphysis; tibial menisci; and articular discs in synovial joints.
Cartilage: Histology and accumulate synovial fluid.
Positioning, orientation Orientation Awareness of oneself in relation to time, place and person. Psychiatric Assessment, and growth of limbs in the developing embryo Embryo The entity of a developing mammal, generally from the cleavage of a zygote to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the fetus. Fertilization and First Week is determined genetically and by the expression of specific timed chemical signals.
Positioning of limbs along the craniocaudal axis Axis The second cervical vertebra. Vertebral Column: Anatomy is determined by the homeobox (HOX) genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure.