Session 3: Self-Study Flashcards
A surgeon makes an incision through the scalp in order to access the sull to perform a craniotomy; what layers would the scalpel blade penetrate?
SCALP
Skin
Connective tissue (loose)
Aponeurosis
Loose connective tissue layer
Periosteum
Following a non-penetrating injury to the scalp, why does the haematoma form a well circumscribed lump?
Within which layer of the scalp has this bleeding likely occurred?
In the dense connective tissue layer.
Because this layer is so dense vessels are confined to compartments within the layer and do not easily penetrate the compartments.
The result is that the damaged vessel will leak blood and to make room for more blood it will leak out into the skin layer instead of out in another compartment.
Following some head injuries involving the scalp blood can track forward causing brusing to appear around the eyes.
Within which layer of the scalp has this bleeding likely occurred?
This is called a subgaleal haematoma (underneath the galeal aponeurosis)
Blood between the aponeurotic layer and the periosteal layer in this potential space.
The blood is not confined to one place here.
Explain why bleeding can be profuse and difficult to stop from an incised scalp wound involving the dense connective tissue layer.
Most of the arteries of the scalp can be found in the dense connective tissue layer. These arteries anastomose a lot and therefore it is hard to stop the bleeding.
Also due to the properties of the dense connective tissue layer the arteries adhere to the walls of the dense connective tissue and this prevents the from constricting in the event of damage.
An incised scalp wound may gape open if the wound involves the aponeurosis; why do such wounds gape, while more superficial scalp wounds do not?
Because the aponeurosis is attached anteriorly to the frontal belly of occipitofrontalis and posteriorly to the occipital belly of occipitofrontalis.
When there is a cut of the aponeurosis the two opposing bellies will pull the aponeurosis in opposite direction.
Following a difficult labour a newborn baby develops a traumatic subperiosteal haematoma also known as cephalohaematoma.
Does this swelling pose a risk to the baby’s brain?
No not really.
The haematoma will be confined to the area on top of one of the cranial bones and will not cross suture lines. This is because the haematoma can be found between the periosteum and the outer table of the skull bone.
This also means that the bleeding extracranial and not intracranial. ICP will therefore not increase.
What limits the spread of bleeding within the subperiosteal layer?
The periosteal layer of the dura closely adheres to the out and inner table of the skull. However bleeding can still occur in between, but at the suture lines the periosteal layers continues to be continuous to line the inner table of the skull.
At these points (reflections) the periosteal layer closely adhere to the inner/outer table of the skull and blood cannot surpass this adhesion.
Why might an infection deep within the scalp, particularly extending beneath the aponeurotic layer, potentially spread intracranially i.e to structures within the cranial cavity of the skull?
These infections roam in the loose connective tissue layer of the scalp and the pathogens can also roam freely here.
The loose connective tissue layer of the scalp also has emissary veins which connect the scalp to the cranial cavity. The emissary veins drain into the dural venous sinuses found intracranially. This means that pathogens can potentially find their way through the emissary veins to go intracranially and infect structures in the cranial cavity.
