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.
What is the functional advantage of having ribs attached to costal cartilage, as opposed to directly articulating with the sternum (bone - bone type articulation)?
Costal cartilage is hyaline cartilage, meaning it provides a degree of flexibility/ elasticity whilst still being semi-rigid. This enables the ribs to move to some degree, which is necessary for respiration.
Describe what is meant by the following general term(s):
Costal margin.
The costal margin is the medial margin formed by the cartilage of the 7th to 10th ribs.
(note: this is the cartilage which connects these vertebrochondral ribs to the costal cartilage of rib 7 above, it is NOT ‘costal cartilage’ as such).
State which ribs are typical, and which are atypical.
What are the characteristics of typical ribs?
Ribs 3-10 are typical, whereas ribs 1, 2, 11 and 12 are atypical.
Typical ribs possess the following features:
-superior and inferior articular demifacets
-head
-crest of head
-neck
-tubercle
-angle
-shaft (including internal and external borders)
-costal groove (housing neurovascular bundle)
Specifically, what do the articular demifacets of ribs articulate with?
The superior articular demifacet of a rib articulates with the vertebral body of the vertebrae above that rib (so if rib we’re looking at rib 5, the SAD articulates with T4).
The inferior articular demifacet of a rib articulates with the vertebral body of its own number (so the IAD of rib 5 articulates with T5).
What does the crest of the head of the rib align with, and why is this surface rough?
The crest of the head of the rib aligns with the intervertebral disc, and it is rough for the attachment of the interarticular ligament.
a. ) Is the crest of the neck of the rib on it’s superior, or inferior border?
b. ) State the textural property of this region (smooth/ rough), including why this is so.
a. ) Crest of neck of rib is on the superior border of the neck of the rib.
b. ) The crest of the neck of the rib is rough, for attachment of the costotransverse ligament.
State the location of the costal groove on the rib. What is the function of this groove?
The costal groove is on the internal surface of the rib, on its inferior border. The costal groove houses the neurovascular bundle.
Describe what is meant by the following general term(s):
Angle of the rib.
The angle of the rib is the region on the rib of greatest curvature. Basically, it is the change in direction of the rib, as it turns anterolaterally.
Explain both the anatomical, and functional significance of the angle of the rib. Is this region rough or smooth?
Anatomically - the angle of the rib is on the exterior surface, and so it is smooth. Anatomically it serves as the most lateral point of attachment for true back muscles.
Functionally - the angle of the rib helps to translate slight rotational movements into elevation or depression, which is useful as the ribs elevate or depress during respiration.
How many facets are found on the head, and tubercle, of the first rib?
Singular facet on the head and tubercle of first rib.
Does the first rib possess a discrete angle?
1st rib lacks a discrete angle.
Does the first rib possess a costal groove?
The first rib lacks a costal groove.
How many facets are found on the head, and tubercle, of the second rib?
Demifacet on the head of the first rib, and singular facet on the tubercle.
Does the second rib possess a discrete angle?
2nd rib does possess discrete angle.
Does the second rib possess a costal groove?
Yes.
What is unique about both the 11th and 12th ribs?
Both the 11th and 12th ribs lack an anterior attachment; only a small tip of costal cartilage is seen.
How can we distinguish between the 11th and 12th ribs?
- 12th rib is shorter then 11th
- 12th rib has no costal groove whereas 11th has shallow costal groove
- 12th rib has no discrete angle whereas 11th has slight discrete angle
Detail the posterior, lateral and anterior attachment points for the superior thoracic aperture.
Anterior - superior border of manubrium.
Posterior - vertebral body of T1.
Lateral - medial border of first rib.
List 3 structures passing through the superior thoracic aperture.
- Oesophagus.
- Trachea.
- Vagus nerve.
Detail the posterior, lateral and anterior attachment points for the inferior thoracic aperture.
Anterior - xiphoid process.
Posterior - vertebral body of T12.
Lateral - inferior border of 12th rib, and tip of 11th rib.
What structure fills the inferior thoracic aperture?
What innervates this structure (BE SPECIFIC)?
The respiratory (thoracic) diaphragm spans the inferior thoracic aperture, which is innervated by the phrenic nerve (from VPR of C3, C4 and C5).
List 3 structures passing through the inferior thoracic aperture, including all of the following:
a. ) the name of the space they pass through.
b. ) the vertebral level at which this occurs.
- Aorta - passes through aortic hiatus, T12.
- Oesophagus - passes through oesophageal hiatus, T10.
- Inferior vena cava - passes through vena caval aperture, T8.
Detail the posterior, lateral and anterior boundaries for the inferior pelvic aperture.
What structure usually fills this space?
Anteriorly - pubic symphysis and pubic arch.
Laterally - ischial tuberosities.
Posteriorly - coccyx.
The pelvic diaphragm usually fills this space.
Name 3 structures which pass through the inferior pelvic aperture.
- Anal canal.
- Urethra.
- Vagina (females only).
