Lecture Notes: Human Excretory System and Comparative Excretion in Animals
Introduction
- Warm welcome to the lecture on a platform providing high-quality education.
- Discussion on the topic of human excretory system and associated structures.
Human Excretory System
- Main excretory organs: Kidneys
- Accessory excretory organs: Lungs, Liver, Skin, Large Intestine
Functions of the Human Excretory System
- Kidneys: Principal organs performing excretion and osmoregulation.
- Skin: Largest excretory organ; sweat gland removal of water, salts, lactic acid. Sebaceous glands remove oil and other metabolic wastes.
- Lungs: Removal of carbon dioxide, water vapor, volatile substances like alcohol and ketones.
- Liver: Converts ammonia to urea via urea cycle; metabolizes steroids, toxins, and drugs.
- Large Intestine: Removes salts of heavy elements.
Excretory Structures in Animals
- Protozoans: Use plasma membrane for excretion.
- Porifera (Sponges): Use canal system for water flow and waste removal.
- Cnidarians and Ctenophora: Body wall carries out excretion.
- Flatworms (Platyhelminthes): Excretion via flame cells.
- Roundworms (Nematoda): Excretion via H-shaped excretory canals.
- Annelids: Use nephridia for excretion.
- Arthropods:
- Insects: Malpighian tubules.
- Crustaceans: Green glands or antennal glands.
- Arachnids: Coxal glands.
- Mollusca: Pericardial glands and organ of Bojanus.
- Echinodermata: Use tube feet for excretion.
- Protochordates and Vertebrates:
- Protochordates: Proboscis gland or nephridia for excretion.
- Vertebrates: Use kidneys.
Comparative Excretion in Animals
- Ammonotelic Animals: Excrete ammonia; requires abundant water. Found in aquatic invertebrates, bony fishes, and amphibian larvae.
- Ureotelic Animals: Excrete urea; less toxic and requires moderate water. Found in mammals, cartilaginous fishes, and adult amphibians.
- Uricotelic Animals: Excrete uric acid; least toxic and requires minimal water. Found in birds, reptiles, and insects.
Detailed Study of Kidneys
- Kidney Structure: Protected by last two ribs; covered by a fibrous capsule.
- Nephrons: Functional units; approximately 1 million per kidney.
- Medulla and Cortex: Parts of kidneys with distinct functions in urine formation.
Conclusion
- Encouragement to participate actively and focus on understanding concepts.
- Surprise announcement of new physics class collaboration.
These notes capture the essence of the lecture, with an emphasis on the structure and functioning of human and comparative animal excretory systems.