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Eyes: How They Work, Anatomy and Common Condition

 The eye is a complex sensory organ that allows us to see the world around us. The eye works by gathering light from the environment and converting it into electrical signals that can be interpreted by the brain. The basic structure of the eye includes the cornea, iris, pupil, lens, retina, and optic nerve. The cornea is the transparent outer layer of the eye that helps to focus incoming light. The iris is the colored part of the eye that regulates the amount of light that enters the eye through the pupil, which is the black circular opening in the center of the iris. The lens is a clear, flexible structure located behind the iris that helps to focus light onto the retina. The retina is a thin layer of tissue that lines the back of the eye and contains photoreceptor cells called rods and cones. These cells convert light into electrical signals that are sent to the brain via the optic nerve. The rods are responsible for the low light vision and detecting motion, while the cones are resp
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Coronary artery disease - Symptoms and causes

      Coronary artery disease



Coronary artery disease (CAD) is the most common type of heart disease in the United States. It is sometimes called coronary heart disease or ischemic heart disease. For some people, the first sign of CAD is heart disease. You and your healthcare team may be able to help reduce your risk for CAD.


Types:

Many people think of Coronary artery disease (CAD)  as plaque buildup in your arteries, or atherosclerosis. But plaque buildup occurs in only one type of coronary heart disease. 
There are three types of coronary heart disease, including: 

*Obstructive coronary artery disease
 
*Nonobstructive coronary artery disease
 
*Spontaneous coronary artery dissection
 

Obstructive coronary artery disease
 
Obstructive coronary artery disease occurs when your coronary arteries gradually narrow due to plaque buildup, also known as atherosclerosis. It’s the type of coronary artery disease that’s most common and well-known. 
As the artery narrowing worsens, it can eventually cut off blood flow to your heart. A sudden blockage is known as a heart attack, which requires immediate medical attention to minimize the heart damage.

Nonobstructive coronary artery disease 

Nonobstructive coronary artery disease occurs because of other problems with your coronary arteries. It’s not caused by plaque buildup. Instead, your coronary arteries may have problems such as:
 
Compression or squeezing from the heart muscle (myocardial bridging)
Constrictions at improper times (coronary vasospasm)
Damage to the artery lining (endothelial dysfunction) 
Malfunctions in smaller artery branches (microvascular dysfunction) 
Nonobstructive coronary artery disease can still cause many of the traditional symptoms of coronary artery disease, such as chest pain or shortness of breath. Many people with nonobstructive coronary artery disease experience angina, or chest pain, related to CAD. While nonobstructive heart disease can develop in anyone, it’s most common in females
.   
Spontaneous coronary artery dissection

Spontaneous coronary artery dissection (SCAD) occurs when a tear in the coronary artery wall partially or completely blocks blood flow. This tear happens suddenly and often presents as a heart attack. 
SCAD and heart attack symptoms can vary from person to person but may include: 
 
Chest pain, especially on the left side or center of your chest that doesn’t go away with rest
Jaw, neck, or back pain  
Lightheadedness or weakness
Pain radiating from your chest through your shoulders or arms
Sensations of fullness, pressure, or squeezing in your chest  
Shortness of breath, even at rest

Symptoms:

Symptoms may go unrecognized at first, or they may only occur when the heart is beating hard like during exercise. As the coronary arteries continue to narrow, less and less blood gets to the heart, and symptoms can become more severe or frequent.

Coronary artery disease signs and symptoms can include:

Chest pain (angina). You may feel pressure or tightness in your chest. Some people say it feels like someone is standing on their chest. The chest pain usually occurs on the middle or left side of the chest. Activity or strong emotions can trigger angina. The pain usually goes away within minutes after the triggering event ends. In some people, especially women, the pain may be brief or sharp and felt in the neck, arm, or back.

Shortness of breath. You may feel like you can't catch your breath.
Fatigue. If the heart can't pump enough blood to meet your body's needs, you may feel unusually tired.

Heart attack. A completely blocked coronary artery will cause a heart attack. The classic signs and symptoms of a heart attack include crushing chest pain or pressure, shoulder or arm pain, shortness of breath, and sweating. Women may have less typical symptoms, such as neck or jaw pain, nausea, and fatigue. Some heart attacks don't cause any noticeable signs or symptoms.

Causes:

Coronary artery disease starts when fats, cholesterols, and other substances collect on the inner walls of the heart arteries. This condition is called atherosclerosis. The buildup is called plaque. Plaque can cause the arteries to narrow, blocking blood flow. The plaque can also burst, leading to a blood clot.
Besides high cholesterol, damage to the coronary arteries may be caused by:

*Diabetes or insulin resistance

*High blood pressure not getting enough exercise (sedentary lifestyle)
Smoking or tobacco use
 

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