6.28.2015

My top 10 diseases

Top 10 diseases:

1.Nodding Syndrome: It is a recent disease which emerged in the 1980s. Little is known about the disease. It is a mentally and physically disabling disease that only affects children, typically between the ages of 5 and 15. It is currently restricted to small regions South Sudan, Tanzania and northern Uganda. Children affected by the disease experience a permanent stunting of growth, this includes growth of the brain. The victims experience pathological nodding seizures which arise as the child begins to eat. It is currently not known what causes the disease but it is believed to be connected to the parasitic worm Onchocerca volvulus, carried by the black fly. 


 
2.Kuru disease: It is an extremely rare and fatal disease which affects the nervous system. It is caused by cannibalism, specifically eating infected brains. It was contracted by the Fore people in the highlands of New Guinea by performing cannibalism during funeral rituals. It is characterised as difficulty walking, swallowing and chewing. Symptoms also include loss of coordination and muscle twitching. The name Kuru translates to "Shiver" or "trembling in fear". It is also known as laughing sickness due to pathological bursts of laughter that the patient displays. 

3.Naegleria Fowleri: Also known as brain eating amoeba, they are found in bodies of fresh water, such as ponds, lakes, rivers and hot springs. It invades the central nervous system via the nose, and migrates to the brain. It feeds on the nerve tissue causing significant necrosis and haemorrhaging. 

4.African Trypanosomiasis: 
Is a parasitic disease also known as the sleeping sickness. The disease initially causes fevers, itchiness, headaches and joint pains. The second stage begins with confusion, poor coordination numbness and trouble sleeping. Invasion of the circulatory and lymphatic systems by the parasites is associated with severe swelling of lymph nodes. The second neurological stage begins when the parasite invades the central nervous system, by passing through the blood brain barrier. Disruption of the sleep cycle is a leading symptom of this stage. Without treatment the disease is invariably fatal, with progressive mental deterioration leading to coma, systemic organ failure and death.   

5.Ebola: It is a viral illness of which the initial symptoms can include a sudden fever, intense weakness, muscle pain and a sore throat. Subsequent stages include: vomiting, diarrhoea and in some cases both internal and external bleeding. The disease infects humans through close contact with infected animals. It then spreads between humans by direct contact with infected blood, bodily fluids or organs, or indirectly through contact with contaminated environments. The virus attacks the lining of blood vessels causing internal organs throughout the body to ooze blood. This includes the lungs therefore resulting in the victim drowning in their own blood.
  

6.HIV virus: It is a virus that can hide in the cells of your body for long periods of time and then attacks a key part of your immune system- your T-cells or CD4 cells which are essential to fight disease. However, HIV hijacks these cells and uses them to replicate, subsequently destroying them. HIV can kill so many of these cells that your body can no longer fight infection, this stage is called AIDS. 

7.Alice In Wonderland Syndrome (AIWS): Also known as Todd's syndrome, is a disorientating neurological condition that affects human perception. It affects the sense of vision, sensation, touch and hearing. A prominent symptom is experiences of altered body image. AIWS also involves perceptual distortions of the size or shape of images. The patient can also lose sense of time, space and velocity. The causes are not known. 

8.FOP: Is a rare genetic disease that affects the connective tissue. The body causes fibrous tissue such as ligament, tendon and muscle, to become ossified, or to change into bone when damaged. This means a fall can cause bone to grow within the muscles and tendons throughout the body. It is the only known disease which causes one type of organ system to turn into an entirely different one. There is no known treatment.


9.Progeria: It is an extremely rare genetic disorder where symptoms associated with ageing are manifested at a very early age. Those born with the disease do not tend to live above the age of 13. It is a genetic condition that occurs as a new mutation, and is rarely inherited, as carriers do not live to reproduce. Symptoms include limited growth, hair loss, and a distinctive appearance. Later the condition causes wrinkled skin, atherosclerosis, kidney failure, loss of eyesight, and cardiovascular problems. People diagnosed with the disease usually have small, fragile bodies, like those of elderly people. It is caused due to abnormal mRNA transcription; this causes an abnormal variant of the prelamin A protein. 


10.Elephantiasis: This disease is caused by parasitic worms which are transmitted by mosquitoes. After bitten by an infected mosquito, the larvae spread. Ultimately, the parasites accumulate in the surrounding tissues. This causes fluid build up which leads to extreme swelling.  






Foetal Circulation - Anatomy and Physiology

Foetal Circulation

Prior to birth the foetus is not capable of respiratory function due to the lungs being full of amniotic fluid, subsequently the foetus relies on the maternal circulation for gas, nutrition and waste exchange. However, the foetal and maternal blood never mix, instead they interfere at the placenta. The foetus' lungs and liver are not functional.

Oxygenated blood travels from the placenta to the foetus via the umbilical vein, within the umbilical cord. Most of it bypasses the liver as the umbilical vein is connected to the caudal vena cava by the ductus venosus. The flow of blood to the heart is controlled by a sphincter. 

Due to the foetus' lungs being dis functional, oxygenated blood does flow through the right ventricle into the pulmonary circulation, but bypasses this route by going from the right atrium straight to the left atrium via the foramen ovale (an opening between the two atria). This enables blood to flow directly into the systemic circulation. The septum secundum directs the majority of the blood entering the right atrium through the foramen ovale into the left atrium. Here it mixes with a small volume of blood returning from the non-functional lungs via the pulmonary veins.

The ductus arteriosus connects the pulmonary artery to the aorta and allows equivalent ventricular function in the foetus. The blood from the right ventricle is pumped to the pulmonary trunk where, due to the high resistance in the collapsed foetal lungs, a larger volume passes through the ductus arteriosus to the caudal aorta. Most of the blood in the aorta is then returned to the placenta for oxygenation through the umbilical arteries. The ductus arteriosus empties blood into the aorta after the artery to the head has branched off thus ensuring that the brain receives well-oxygenated blood. 

The two cardiac shunts I have talked about are:

  • Connection between the right and left atria via the foramen ovale
  • Connection between the pulmonary pulmonary artery and aorta via the ductus arteriosus









Changes at Birth

Important circulatory changes occur at birth due to the replacement of the placenta by the lungs as the organ of respiratory exchange. When an newly born animal takes its first breath, the lungs and pulmonary vessels expand thereby significantly lowering the resistance to blood flow. This subsequently lowers the pressure in the pulmonary artery and the right side of the heart. On the other hand the removal of the placenta causes an increase in the resistance of the systemic circulation and hence an increase in the pressure of the left side of the heart.

With birth a change from parallel flow to a serial one requires the following changes to take place:
  • Gas exchange takes place in lungs in place of the placenta
  • By cutting the umbilical cord, the placental circulation system is switched off
  • The foetal heart shunts become closed
With the activation of breathing the lungs becomes distended, the capillary network dilated and their resistance is reduced drastically so that a rich flow of blood can take place. As a consequence, the pressure in the right atrium sinks in comparison with that of the left one. This pressure turnaround in the atria causes the septum primum to be pressed against the septum secundum and the foramen secundum becomes functionally closed. Additionally, the pressure in the aorta is now higher than that in the pulmonary artery thus decreasing blood flow in the wrong direction. After a few weeks, the shunt via the ductus arteriosus is obliterated. 

























Diseases which result from defects in this process

  • Pre-eclampsia: It is a combination of hypertension and proteinurea. It can potentially progress to a condition called eclampsia, which can cause fits or convulsions. Symptoms include: severe headaches, problems with vision, severe pain just below ribs, heart burn and rapid swelling of face, hands and feat. The exact cause of pre-eclampsia remains unknown but research indicates that genetics and the placenta could be factors in the development of pre-eclampsia. High blood pressure is very dangerous during pregnancy as it may interfere with the placenta's ability to delivery oxygen and nutrients to the foetus. It also can cause abnormal renal and liver functioning. Also, it can cause destruction of red blood cells and platelets which can result in spontaneous bleeding as clotting factors decrease. The high blood pressure can also cause the placenta to begin to pull away from the uterus wall ( placental abruption). This can cause severe bleeding an even death. Also, the mother can experience seizures which puts the foetus at risk of deprived oxygen. 
  • Uterine rupture: It is when the scar from your previous caesarian section tears open. It is possible for your scar to gape slightly (scar dehiscence) but this is unlikely to cause problems for the mother or the baby. Uterine rupture, however, can be life threatening for the foetus as it puts it at risk of oxygen deprival. This is common in african women as caesarians are not carried out properly, putting the uterus at a higher risk of rupturing.