Summary
Highlights
The video revisits the human excretory system, highlighting the four main organs: lungs (paru-paru), kidneys (ginjal), liver (hati), and skin (kulit). It notes that lungs are covered in the respiratory system, kidneys were discussed previously, and this video will focus on the liver and skin as excretory organs.
The liver, also known as hepar, has several vital functions. It excretes urea, breaks down old red blood cells (erythrocytes) using Kupffer cells, and is the site of deamination, which converts toxic ammonia into less harmful urea. The liver also has self-protection capabilities through phagocytosis, secretes bile to emulsify fats for digestion, neutralizes toxins, and plays a role in carbohydrate metabolism (storing and breaking down glycogen).
The liver consists of two lobes: a larger right lobe and a smaller left lobe. It also contains the gallbladder (vesica fellea), which stores bile. Blood supply to the liver comes from two main vessels: the hepatic artery (arteri hepatica), which brings oxygen-rich blood, and the hepatic portal vein (vena porta hepatica), which carries nutrient-rich but potentially toxic blood from the intestines. The liver processes this blood, removing toxins and utilizing nutrients, before it exits via the hepatic vein (vena hepatica) to the heart.
The video details the breakdown of old red blood cells (erythrocytes) in the liver after about 120 days. Hemoglobin from these cells is broken down into three components: iron (Fe), globin, and heme. Iron and globin are recycled to form new red blood cells. Heme is converted into biliverdin, then bilirubin, and finally urobilin. Urobilin is excreted with bile, contributing to the color of feces, and some is reabsorbed and excreted in urine, giving urine its characteristic color.
Deamination is the process where the liver breaks down proteins, producing amino acids and a toxic byproduct called ammonia (NH3). To neutralize ammonia, the liver converts it into urea through a cyclical process. Ammonia reacts with ornithine and carbon dioxide to form citrulline. Citrulline then reacts with more ammonia to form arginine. Arginine, with the help of the enzyme arginase, breaks down into water, urea, and ornithine, allowing the cycle to continue. Urea is then transported to the kidneys for excretion in urine.
The video discusses several liver-related disorders: Gallstones (batu empedu) are deposits of cholesterol in the bile ducts, often caused by high-fat diets, leading to blockages and severe pain. Jaundice (penyakit kuning) is a condition caused by excessive bilirubin buildup in the blood and tissues, making the skin and eyes appear yellow. Hepatitis is inflammation of the liver caused by viruses, autoimmune conditions, excessive alcohol consumption, or strong medications. Cirrhosis (pengerasan hati) is the irreversible scarring of liver tissue, leading to a drastic decrease in liver function and potential mortality.
Visual examples are provided to illustrate the discussed liver diseases. Jaundice is shown with a patient exhibiting yellowed eyes, indicating bilirubin accumulation. Gallstones are depicted as hard deposits within the gallbladder. Finally, a comparison of a healthy liver and a cirrhotic liver highlights the hardened, scarred surface of the diseased organ, emphasizing the permanent damage it sustains.