Week 1 Content Flashcards
Name the four somatic systems.
Skeletal system, articular system, muscular system, integumental system. (S.A.M.I)
Name the four visceral systems.
Cardiovascular & respiratory system, reproductive system, urinary system, gastrointestinal system. ((C.R.)R.U.G.)
Name the four supply systems.
Nervous system, arterial system, venous system, lymphatic system. (N.A.V.L.)
Internal rotation is also known as what kind of rotation?
Medial rotation.
External rotation is also known as what kind of rotation?
Lateral rotation.
Congenital diseases are also known as what?
Birth defects.
Birth defects are only structural. True or false?
False. Birth defects can be both structural and functional.
Congenital diseases are present at or before birth. Approximately how many babies are born with birth defects?
3%.
Congenital diseases arise from genetic factors alone. True or false?
False. Birth defects occur due to environmental, infectious, nutritional or genetic reasons.
List at least 3 examples of congenital diseases.
Any 3 of:
- Heart defects
- Orofacial clefts
- Trisomy 21 (Down Syndrome)
- Polydactyly
- Neural tube defects
List and define the three periods of human embryology.
- “Fertilized egg”/”Conceptus” - Fertilization to the end of the 2nd week.
- “Embryo” - Beginning of 3rd week to the end of the 8th week.
- “Fetus” - 3rd month to birth.
Outline the early stages of embryological development.
- Ovulation - a secondary oocyte is released from the ovary and is swept into the oviduct.
- Fertilization - a single sperm penetrates the secondary oocyte. Eventually, the sperm and egg nuclei will fuse to form a zygote.
- Cleavage - the zygote undergoes rapid mitotic cell division as it moves along the oviduct towards the uterus, becoming a pre-embryo consisting of 2 cells, then 4 cells, then 8 cells and so on.
- Morula - by day 4, successive divisions produce a morula, a solid ball of cells that enters the uterus.
- Blastocyst - by day 6, the pre-embryo becomes a blastocyst, a hollow ball of cells with a fluid-filled cavity. The blastocyst has freed itself from the zona pellucida and can increase in size.
- Implantation - the blastocyst attaches to the uterine lining (endometrium) and begins to digest its way inwards. The cells of the inner cell mass begin to form primary germ layers.
Briefly outline the composition of a blastocyst.
A blastocyst has an outer epithelial layer known as the trophoblast. It has a bundle of cells within its cavity known as the inner cell mass.
The trophoblast forms what?
The trophoblast forms extra-embryonic structures (part of placenta).
When does a blastocyst implant into the uterine wall?
Between days 5 and 10.
A late blastocyst is a 3 germ layer stage. True or false?
False. A late blastocyst is a 2 germ layer stage. The inner cell mass splits and forms cavities and the embryonic disk.
What are the two main functions of gastrulation?
To form the primitive streak which defines all of the major body axes and to form the three primary germ layers (ectoderm, mesoderm and endoderm). These three layers give rise to distinct tissues in adults.
Briefly outline the processes of gastrulation.
During gastrulation, a line of thickened cells appear on the epiblast. This is the primitive streak. The primitive streak invaginates to form the primitive groove.
In order for the three germ layers to form, cells must migrate medially and into the primitive groove. First, cells from the epiblast move into the hypoblast to form embryonic endoderm. Next, cells migrate into the space between the endoderm and the epiblast to form embryonic mesoderm. The remaining cells of the epiblast form embryonic ectoderm. The embryo is now trilaminar.
How do body axes differ between embryos and adults?
In embryos, the cranial direction is anterior and the caudal direction is posterior. In adults, the cranial direction is superior and the caudal direction is inferior.
Which structure is vital in setting up left-right asymmetry in the body?
The node.
Which hypothesis best accounts for the formation of left-right asymmetry in the body?
(a) Morphogen hypothesis
(b) Nodal vesicular parcel hypothesis
(c) Two cilia hypothesis
(c) Two cilia hypothesis
Briefly outline the two cilia hypothesis.
Cilia within the node rotate. As there is leftward fluid flow, only cilia to the left detect the flow. This triggers a response in which left-right asymmetry is induced.
What is situs inversus and how frequently does it occur?
Situs inversus is a condition in which organs are mirrored from their regular position. Organs may only be partially mirrored, and in certain cases only some organs are mirrored. Heart defects are a problem commonly associated with situs inversus. Situs inversus occurs in approximately 1:8000.
What is the notochord?
The notochord is cartilage-like transient structure which is important for induction of the neural tube.
How does the notochord form?
There is cranial midline extension from the primitive node and a hollow tube forms. The tube grows in length as cells are added from the primitive node and the primitive streak regresses.
What complication may result if the primitive streak does not regress?
A teratoma may result if the primitive streak does not regress. This is a benign tumour that can be corrected via surgery. Teratomas are the most common tumour in new borns, occuring in 1:35000 births.
