Answer to follow later this week!
Answer to follow later this week!
Infarction is death of tissue because the supply of oxygen is cut off. Typically this occurs because a blood vessel is blocked. Causes of blockages include thrombi (clots), bacterial emboli (bits of abscess that break off into the bloodstream), and tumour emboli (bits of tumour which break off into the bloodstream).
Because more than one vessel might supply a tissue an infarction will only occur if i) all the vessels are blocked at once, or ii) the area is supplied by a single artery (also called an ‘end arterial supply’). One organ predisposed to infarction due to having an end arterial supply is the kidney.
At post mortem examination a recent (acute) infarction will be visible as a really well demarcated zone of reddening. This reddening corresponds with the area supplied by the blocked vessel(s).
Over time, the dead tissue is replaced by fibrous tissue (scar tissue) which contracts downwards to leave an indentation.
This kidney has an acute infarction; the dark red wedge on the cranial (top) pole of the kidney. And a more longstanding (chronic) infarction; the indentation on the caudal (bottom) pole of the kidney, where you can see the remnants of the dark red discolouration.
Can you guess what this is? Tissue from a dog. Answer to follow later this week!
Last week we asked you to identify the pigment (orange arrows) and elliptical material (black arrows) in this image.
This tissue is from a foal which was born dead. The pigment is meconium – the faeces passed by a foetus when it is in the uterus. The elliptical material are scrolled skin cells, called squames, which are shed by the foetus during pregnancy. They are refractile, as can be seen in the next image of the same area of lung using polarised light.
The pink feathery material is protein rich fluid (amniotic fluid). These findings are consistent with aspiration of amniotic fluid by the foal because of distress, drawing meconium, dead skin cells and aminiotic fluid deep into the lungs as it gasps. This might be due to a twisted umbilical cord, for example.
Here is a picture from the lungs of a foal (H&E, x400). The alveolar capillaries are distended by red blood cells (congestion). Do you know what the granular pigment (orange arrows) and elliptical material (black arrows) are? The answer will be revealed early next week!
Horse bot flies have a life cycle which is not very pleasant for the poor horse. The adult fly will lay her eggs on the hairs of the horse’s front-half (front legs, chest, shoulders and sides). After the first stage of the larvae has formed within the egg, the action of licking at the area by the horse prompts them to emerge. These larvae will then migrate to the mouth, or enter the mouth during licking, and embed themselves in the horse’s tongue. They sit in the soft tissues of the mouth for about a month before they moult into their second stage. They then crawl into the stomach and attach to the lining where they complete their growth and moulting into the third larval stage. They stay here for about a year, before detaching and passing out with the manure, where they will pupate and then hatch as adult flies a few weeks later…
Whilst they are migrating through the horse’s body they can cause irritation of the mouth and gastrointestinal tract. In large enough numbers they may even cause a blockage. Stomach ulcers, stomach rupture, oesophageal paralysis, and even tumours may result from the long standing infestation by these critters.
Do you know what these creepy fellows are? Bonus points if you know the species and organ they are found on…