Human Physiology and Anatomy

Rickets is a bone disease caused by vitamin D deficiency, calcium deficiency, or phosphate deficiency in children. It leads to soft and weak bones, skeletal deformities, and impaired growth.

The plasma membrane (cell membrane) primarily regulates the transport of materials in and out of the cell through selective permeability. It does not control all cellular activities (that's the nucleus), store materials (that's vacuoles), or maintain shape alone (that's the cell wall in plants).

When walking downhill, your knees must absorb significantly more force due to gravity and the braking motion required to control your descent. Biomechanics studies confirm that knee pressure can reach approximately 3-4 times body weight during steep downhill walking.

The gallbladder's primary function is to collect and store bile produced by the liver. It does NOT produce bile (that's the liver's job), filter calcium (that's kidneys), or filter toxins (that's the liver). The gallbladder concentrates and stores bile for release during digestion.

The pancreas is described as pistol-shaped in anatomy due to its distinctive structure - a head near the duodenum, a body crossing the abdomen, and a tail extending toward the spleen, resembling a pistol's grip and barrel. The liver, brain, and heart have different shapes.

Finger ridges evolved to enhance friction and grip. They function like tire treads, helping us grasp objects securely by increasing surface area and providing mechanical advantage. The other functions listed are incidental benefits, not the primary evolutionary purpose.

Fingernails and toenails are made of dead skin cells that have been compressed and filled with keratin protein. They are NOT made of calcium or minerals (a common misconception). This keratin makes nails hard and protective.

Fingernails and toenails are primarily composed of a tough protective protein called keratin - the same protein found in hair and the outer layer of skin. Keratin provides nails with their strength and durability.

The brain relies almost exclusively on glucose for its energy requirements, as it cannot use fatty acids or other fuels directly. Under normal conditions, glucose is the primary substrate for brain metabolism, though it can use ketone bodies during fasting.

CPR stands for Cardio Pulmonary Resuscitation. It is an emergency procedure combining chest compressions with artificial ventilation to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person who is in cardiac arrest.

The risk of male-to-female transmission of HIV during sexual intercourse is actually higher than female-to-male transmission. Therefore, the statement claiming female-to-male transmission is twice as likely is incorrect.

The pituitary gland, often called the 'master gland,' is the smallest gland in the human body - approximately the size of a pea (about 0.5 grams) and located at the base of the brain. Despite its small size, it produces and regulates numerous hormones that control other endocrine glands and bodily functions. The liver is much larger, the thyroid is also small but larger than the pituitary, and salivary glands are visibly larger.

Hemoglobin is the iron-containing protein in red blood cells responsible for transporting oxygen from the lungs to body tissues and returning carbon dioxide. While it contains iron, its primary function is oxygen transport, not iron utilization per se. Bacteria destruction and anemia prevention are not its direct functions.

Nails are primarily made of keratin, a fibrous structural protein. Keratin is also found in hair and the outer layer of skin. Iron and sodium are minerals, and caffeine is a stimulant compound, not structural components.

The primary function of kidneys is to filter blood and remove waste products and excess substances from the body, producing urine. While kidneys do help regulate blood pressure indirectly through the renin-angiotensin system, their main purpose is waste removal and filtration, not blood pressure control directly.