Lesson Notes By Weeks and Term v5 - Grade 10
Organs and systems of the human body – Week 2 focus
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Organs and systems of the human body – Week 2 focus
Download the Lessonotes Mobile South Africa app for faster lesson access on Android and iPhone.
Subject: Life Sciences
Class: Grade 10
Term: 2nd Term
Week: 2
Theme: General lesson support
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This week, we delve deeper into the fascinating world of the human body, focusing specifically on the digestive, respiratory, and excretory systems. Understanding these systems is crucial because they are fundamental to our survival and well-being. Poor diet (linked to the digestive system) is a major contributor to health problems in South Africa, including obesity and malnutrition. Respiratory diseases, like tuberculosis (TB) and asthma, are also prevalent, highlighting the importance of understanding how our lungs work. Finally, a properly functioning excretory system is essential for removing waste and maintaining a healthy internal environment.
2.1 The Digestive System: Fueling the Body The digestive system is responsible for breaking down food into smaller molecules that can be absorbed into the bloodstream and used by the body for energy, growth, and repair. It consists of the alimentary canal (a long tube from the mouth to the anus) and accessory organs.
Organs and their Functions: Mouth: Mechanical digestion (chewing) and chemical digestion (saliva containing amylase breaks down starch).
Example: Think of pap (maize porridge). Chewing it well starts the digestion process. Amylase in saliva begins to break down the starch in the pap into simpler sugars.
Oesophagus: A muscular tube that transports food from the mouth to the stomach via peristalsis (wave-like muscle contractions).
Stomach: Stores food and continues mechanical digestion (churning). Glands in the stomach lining secrete gastric juice, which contains hydrochloric acid (kills bacteria and provides an acidic environment) and pepsin (an enzyme that breaks down proteins).
Example: The acidity of the stomach helps digest the biltong we eat.
Small Intestine: The primary site of nutrient absorption.
It consists of three sections: the duodenum, jejunum, and ileum. The duodenum receives secretions from the pancreas (digestive enzymes and bicarbonate) and liver (bile). The jejunum and ileum have villi and microvilli to increase surface area for absorption.
Pancreas: Secretes pancreatic juice containing enzymes like amylase (digests carbohydrates), lipase (digests fats), and protease (digests proteins). Also secretes bicarbonate to neutralize stomach acid.
Liver: Produces bile, which emulsifies fats (breaks them down into smaller droplets) to aid in digestion.
Gallbladder: Stores and concentrates bile.
Large Intestine: Absorbs water and electrolytes from undigested material. Forms and stores faeces.
Rectum: Stores faeces until elimination.
Anus: Opening for elimination of faeces.
Enzymes and Digestion: Enzymes are biological catalysts that speed up chemical reactions. Digestive enzymes break down large food molecules into smaller ones: Amylase: Breaks down carbohydrates (starch) into sugars. Protease (e.g., pepsin, trypsin): Breaks down proteins into amino acids.
Lipase: Breaks down fats into fatty acids and glycerol.
Imagine you eat a vetkoek (fried dough) filled with mince (ground beef).
Mouth: Amylase in saliva starts breaking down the carbohydrates in the vetkoek.
Stomach: Pepsin in the stomach starts breaking down the proteins in the mince. The vetkoek and mince are churned.
Small Intestine: Pancreatic amylase further breaks down the vetkoek, lipase breaks down the fats in the vetkoek, and protease (from the pancreas) further breaks down the proteins in the mince. Nutrients are absorbed into the bloodstream.
2.2 The Respiratory System: Breathing Life
The respiratory system is responsible for taking in oxygen and expelling carbon dioxide, a waste product of cellular respiration.
Organs and their Functions:
Nasal Cavity: Filters, warms, and moistens incoming air.
Pharynx: Common passageway for air and food.
Larynx: Voice box; contains vocal cords.
Trachea: Windpipe; carries air to the lungs.
Bronchi: Two branches of the trachea that enter the lungs.
Bronchioles: Smaller branches of the bronchi within the lungs.
Alveoli: Tiny air sacs in the lungs where gas exchange occurs. They have thin walls and a large surface area, surrounded by capillaries.
Mechanism of Breathing:
Inhalation (inspiration): The diaphragm (a muscle beneath the lungs) contracts and moves downwards, and the rib muscles contract and pull the ribs upwards and outwards. This increases the volume of the chest cavity, decreasing the pressure inside the lungs. Air rushes into the lungs to equalize the pressure.
Exhalation (expiration): The diaphragm and rib muscles relax. The volume of the chest cavity decreases, increasing the pressure inside the lungs. Air is forced out of the lungs.