Lab 1 Flashcards
Describe what is meant by the following general term(s):
Cleavage.
The rapid mitotic divisions of the zygote, resulting in an increase in cell number and decrease in cell size. A decrease of cell size occurs as the zona pellucida (exterior glycoprotein layer) encapsulates the cell, limiting its overall size.
What do the following structures become:
a. ) Inner cell mass
b. ) Outer cell mass
c. ) Blastocyst cavity
a. ) Inner cell mass - embryo.
b. ) Outer cell mass - extraembryonic tissues.
c. ) Blastocyst cavity (fluid filled space) - yolk sac.
In what week do the epiblast and hypoblast become apparent? At this stage, what is the developing embryo known as?
Week 2; the bilaminar disc.
In what week is the trilaminar disc formed - and what tissues are derived from these primary 3 germ layers?
Trilaminar disc formed in week 3.
- Ectoderm - epidermis, NS, hair, nails, sebaceous glands.
- Mesoderm - majority of connective/ muscle tissue of body (axial and appendicular skeletons, including the associated muscles/ CT structures of such), dermis, kidneys, gonads, heart and circulatory system.
- Endoderm - lining of GIT (excluding mouth and anus), lining of lungs, liver, pancreas, urinary bladder.
Briefly detail the process by which the long axis of the body is developed.
The process of development of the long axis is known as GASTRULATION:
- Cells from the epiblast migrate through an opening known as the primitive streak.
- These cells differentiate to form the notocord, which is a rod like structure growing deep in mesodermal layer.
- Notocord elongates the trilaminar disc, producing a distinct long axis with cranial and caudal ends. This forms the template for bilateral symmetry of the body.
What classification of bone is the sternum? Explain how this bone forms, including when it is finished forming.
The sternum is a flat bone, which forms through the process of segmental endochondral ossification. This means distinct ossification centres exist throughout it; specifically there is 1 in the manubrium, 4 in the body and 1 in the xiphoid process.
These ossification centres do not completely fuse until the age of 25.
Describe the 5 surface landmarks created by the sternum, including the specific vertebral levels at which they exist.
- Suprasternal (jugular) notch - T2.
- Manubrium - T3, T4.
- Sternal angle - T4/T5.
- Body of sternum - T5, T6, T7, T8, T9.
- Epigastric fossa - T9.
Detail the textural properties (smooth or rough) for the following regions, including in your answer why this is so:
a. ) Clavicular notch
b. ) 1st costal notch
c. ) 2nd costal notch
a. ) Clavicular notch - smooth, for synovial articulation with clavicle.
b. ) 1st costal notch - rough, for cartilaginous attachment with first rib.
c. ) 2nd costal notch - smooth (demifacet), for synovial articulation with second rib.
Detail 3 important landmarks occurring at the sternal angle (T4/ T5)?
- Bifurcation of the trachea.
- Arching of the aorta.
- Drainage of the azygous vein into the superior vena cava.
Describe the concavity/ convexity of the anterior, and posterior aspects of the sternum.
The anterior aspect is convex whereas the posterior surface is concave.
Which ribs attach to the body of the sternum?
All of ribs 3-6 fully attach to the body of the sternum (facet joints), whereas half of ribs 2 and 7 attach to the body of the sternum (demifacet joints).
What material is the ‘xiphoid process’ of the sternum made of?
Generally, by what age does the xiphoid process complete ossification?
The xiphoid process is composed primarily of hyaline cartilage with a core of bone, which completes ossification by 40 years old.
a. ) What surface landmark is found at the level of the xiphoid process, and at what vertebral level does this occur?
b. ) What important nervous structure is found at this level?
a. ) The epigastric fossa, found at T9.
b. ) The celiac plexus.
Which rib(s) articulate with the xiphoid process?
Half of rib 7 only.
Which ribs have costal cartilages?
The vertebrosternal ribs, 1-7.
