Kelas 11 SMA - Biologi - Sistem Ekskresi - Bimbel Tridaya Online

Excretory System Organs and Functions
📌 The excretory system involves the removal of waste products the body no longer needs, primarily through the skin (kulit), liver (hati), lungs (paru-paru), and kidneys (ginjal).
💧 The skin functions as a sensory organ and regulates body temperature by secreting sweat (keringat).
⚖️ The liver is crucial for digestion (emulsifying fats), detoxifying, storing excess sugar as glycogen, and breaking down old red blood cells (erythrocytes) into components like bilirubin and iron (Fe).
💨 The lungs excrete waste by releasing CO₂ through respiration, which is transported in the blood as dissolved $\text{CO₂}$, carbaminohemoglobin ($\text{HbCO₂}$), or carbonic acid ($\text{H₂CO₃}$).

Skin Structure and Sweat Secretion
🔬 The skin has three main layers: Epidermis, Dermis, and Hypodermis.
🛡️ The Epidermis includes the stratum corneum (dead cells), stratum lucidum, stratum granulosum, and stratum germinativum (actively dividing cells).
🌡️ Vasodilation (pelebaran pembuluh darah) occurs when body temperature rises, promoting sweat secretion, regulated by hormones like bradykinin and the hypothalamus.

Kidney Function and Urine Formation
⚙️ The kidneys primarily regulate water balance and blood volume. They consist of the cortex (outer) and medulla (inner), housing the nephrons.
🧪 Urine formation involves three main processes: Filtration (Filtrasi) in the glomerulus, Reabsorption (Reabsorpsi) in the renal tubules, and Augmentation (Augmentasi) in the collecting duct.
🩸 Filtration separates plasma from large molecules like red blood cells ($\text{eritrosit}$) and platelets. Reabsorption brings back essential substances like glucose, amino acids, vitamins, water, and minerals.

Factors Affecting Urine Output and Disorders
📉 Urine output is influenced by Antidiuretic Hormone (ADH), which controls water reabsorption; lower ADH leads to excessive dilute urine output, known as diabetes insipidus.
🌡️ Environmental temperature affects excretion: low temperatures lead to decreased urine output, while high temperatures increase sweat and potentially decrease urine output.
🏥 Common kidney disorders include diabetes insipidus (excessive urination), diabetes mellitus (high blood sugar/glucose exceeding reabsorption capacity), polyuria (high urine volume), and anuria (no urine production).

Key Points & Insights
➡️ The liver processes urea formation via the Ornithine cycle, converting ammonia ($\text{NH₃}$) into urea.
➡️ Reabsorption in the kidney is divided into obligatory (e.g., glucose, amino acids) and facultative (e.g., water, $\text{Na}^+$) based on the body's immediate needs.
➡️ Hematuria (blood in urine) indicates damage to the glomerulus where blood cells are incorrectly filtered out.

📸 Video summarized with SummaryTube.com on Feb 08, 2026, 03:12 UTC