Early embryonic development and cell types

describe the horseshoe-shaped intraembryonic coelom

The horseshoe-shaped intraembryonic coelom is also bent. The future pericardial cavity lies ventrally. The pericardiaco-peritoneal canals lie dorsal to the septum transversum and eventually form the pleural cavities.

what are the different types of stem cells?

Totipotent - can give rise to all cell types found in the adult organism, plus extraembryonic cells e.g zygote Pluripotent - can give rise to all 3 of the germ layers, but not extraembryonic e.g cells of the inner cell mass of the blastocyst - from where embryonic stem cells are derived. As development proceeds, stem cells may lose their pluripotency Multipotent - can give rise to a restricted number of different cell types e.g stem cells of blood-forming tissues and adult stem cells (are found in some tissues e.g. bone marrow, muscle and can generate replacement cells but only of the same or similar type)

What are the body cavities?

The pericardial cavity houses the heart The pleural cavity houses the lungs The peritoneal cavity houses the gut tube

what are the benefits of studying stem cells

But embryonic stem cell-based therapies can do much more than adult. Studying how stem cells develop into heart muscle cells could provide clues about how we could induce heart muscle to repair itself after a heart attack. •The cells could be used to study disease, identify new drugs, or screen drugs for toxic side effects.

What is regulative development?

Differentiation of cells is brought about by both internal cellular factors as well as extracellular factors. Regulative development involves the interaction of adjacent cells, within "embryonic (morphogenic) fields". This gives flexibility to differentiation.

the mesoderm gives rise to?

Paraxial mesoderm Muscles of head, trunk, limbs Skeleton, dermis, connective tissue Head mesoderm Skull, connective tissue, dentin Intermediate mesoderm Urinogenital system, gonads, ducts, accessory glands Lateral mesoderm Connective tissue and muscle of viscera, serous membranes, heart, blood, spleen, adrenal cortex

Lateral folding

Sides come together to form a tube Need to bring ectoderm around so it can provide covering

The ectoderm gives rise to

Surface of body eg Skin, hair, nails, mammary glands, ant. pituitary Neuroectoderm Neural crest (ganglia, adrenal medulla, pigment cells, pharyngeal arch cartilage, head mesenchyme and connective tissue, parts of heart) Neural tube(CNS, retina, pineal, post. pituitary)

define embryonic differentiation

The process during which embryonic cells specialize and diverse tissue structures arise, each with specific functions in the body. In very early embryonic development, the embryo does not possess these varied cells. Differentiation of cells during embryogenesis is the key to cell, tissue, organ, and organism identity. The zygote divides into multiple cells in a process known as cleavage, triggering the beginning of embryonic differentiation. This zygotic division produces blastomeres which later make up the hollow sphere known as the blastocyst. Cells migrate within the blastocyst to locations that will later define the structure of the embryo and consequent organism. In the process, called gastrulation, three germ layers arise the endoderm, mesoderm, and ectoderm.

abornmal zygotes

§The exact number of abnormal zygotes formed is unknown §usually lost within 2 to 3 weeks of fertilization, before the woman realizes she is pregnant, and therefore are not detected. §Estimates are that as many as 50% of pregnancies end in spontaneous abortion §half of these losses are a result of chromosomal abnormalities. §Abortions are a natural means of screening embryos for defects §reduce the incidence of congenital malformations. §without, approximately 12% instead of 2% to 3% of infants would have birth defects. § With the use of a combination of IVF and polymerase chain reaction, molecular screening of embryos for genetic defects is being conducted. §single blastomeres from early-stage embryos can be removed, and their DNA can be amplified for analysis.

What are embryonic stem cells?

•Derived from the inner cell mass of the embryo - pluripotent - can form virtually any cell or tissue type ØPotential for curing a variety of diseases eg: Ødiabetes ØAlzheimer and Parkinson diseases Øanemias Øspinal cord injuries • ES cells may be obtained from embryos after IVF, a process called reproductive cloning. ØMay causes immune rejection but could be modified to circumvent this problem. ØEthical considerations, as the cells are derived from viable embryos.

What are Adult stem cells?

•Restricted in their ability to form different cell types and, therefore, are multipotent, not pluripotent •Scientists are finding methods to circumvent this disadvantage. •Disadvantages of the approach include the slow rates of cell division and their scarcity. Mature (adult) stem cells may replace tissue that is damaged by disease or injury: Øreplace neurons damaged by spinal cord injury, stroke, Alzheimer's disease, Parkinson's disease or other neurological problems; Øproduce insulin that could treat people with diabetes Øheart muscle cells that could repair damage after a heart attack ØPotentially replaces virtually any tissue or organ that is injured or diseased.

how does therapeutic cloning or somatic nuclear transfer works

•Therapeutic cloning or somatic nuclear transfer". ØNuclei from adult cells (e.g., skin) and introduce them into enucleated oocytes. ØOocytes are stimulated to differentiate into blastocysts, and ES cells are harvested. ØBecause the cells are derived from the host, they are compatible genetically, and because fertilization is not involved, the technique is less controversial.

the endoderm gives rise to?

Epithelia of internal surfaces eg Respiratory system Alimentary system Urinary system

the extra embryonic coelom gives rise to

The extra-embryonic coelom persists in the umbilical cord proximally for a time and is important in the development of the gut.