The Immune System's Components and Functions

The immune system consists of active and adaptive components that work together to protect the body from pathogens.

The active immune system includes physical and chemical barriers like mucus, saliva, skin, stomach acid, and blood clots. These form the body's first line of defense against invaders.

The adaptive immune system has two main parts:

1. The humoral response, which uses B lymphocytes
2. The cell-mediated response, which uses T lymphocytes

Vocabulary: B lymphocytes are white blood cells that mature in bone marrow and produce antibodies to fight pathogens.

Vocabulary: T lymphocytes are white blood cells that mature in the thymus gland and directly attack infected cells.

Stem cells found in bone marrow give rise to both B and T lymphocytes. B lymphocytes produce plasma cells, which secrete antibodies into the blood and other bodily fluids.

Definition: Antibodies are proteins made of 4 peptide chains $2 heavy and 2 light$ that can bind to specific antigens on pathogens.

Pathogens can affect plants and animals through various transmission routes, including water, air, direct contact, bodily fluids, insects, and food.

Highlight: A healthy diet, good hygiene, vaccines, and appropriate use of antibiotics all help prevent disease by supporting the immune system.

Fighting Disease: The Body's Defense Mechanisms

The body employs multiple layers of defense to fight disease, starting with the skin as the first barrier. The immune system, particularly white blood cells, plays a crucial role in identifying and eliminating pathogens.

White blood cells constantly patrol the bloodstream for invaders. When they encounter a pathogen, they have three main methods of attack:

1. Ingestion: Phagocytes, a type of white blood cell, engulf and digest foreign cells using enzymes.
2. Antibody production: B lymphocytes produce specific antibodies to target pathogens.
3. Antitoxin production: The immune system generates substances to neutralize toxins produced by pathogens.

Example: Phagocytes have flexible membranes that allow them to surround and engulf foreign particles, much like how a bubble might enclose an object.

Infectious diseases are caused by pathogens entering the body. These pathogens can be:

• Bacteria
• Viruses
• Fungi
• Protozoans
• Prions
• Worms

Definition: Infectious diseases are those caused by pathogens, while non-infectious diseases have other causes such as genetics or environmental factors.

Bacterial infections can cause various diseases, including tuberculosis $TB$ and chlamydia. TB affects the lungs and is spread through respiratory droplets, while chlamydia is a sexually transmitted infection that can lead to infertility if left untreated.

Highlight: Antibiotics are effective against bacterial infections, but it's crucial to complete the full course of treatment as prescribed.

Viral infections involve non-living entities that hijack host cells to replicate. Examples include:

• HIV $Human Immunodeficiency Virus$: Attacks T helper cells, leading to AIDS.
• HPV $Human Papillomavirus$: Causes warts and can be spread through skin-to-skin contact.

Vocabulary: Pathogens are disease-causing organisms, including bacteria, viruses, fungi, worms, protozoa, and prions.

Types of Pathogens and Non-Infectious Diseases

Pathogens come in various forms, each with unique characteristics:

1. Fungal pathogens: Living organisms from the fungus kingdom, including mushrooms, yeasts, and molds. They can be single-celled or form complex networks.
2. Protozoa: Single-celled eukaryotic organisms. For example, Toxoplasma gondii causes toxoplasmosis, which can be dangerous for people with weakened immune systems.
3. Worms: Parasites that live off their hosts. Tapeworms, for instance, can attach to the gut wall and cause abdominal pain and weight loss.
4. Prions: Incorrectly folded proteins that can cause normal proteins to misfold, leading to various diseases.

Example: Tapeworms can be transmitted through undercooked pork. They attach to the intestinal wall and absorb nutrients, potentially causing weight loss in the host.

Non-infectious diseases include allergies, autoimmune diseases, and cancer. These are not caused by pathogens but by other factors such as genetics or environmental triggers.

Cancer is a complex disease caused by changes in DNA that lead to uncontrolled cell growth. Factors that can contribute to cancer development include:

• Radiation $e.g., ultraviolet light, X-rays, gamma rays$
• Carcinogens $chemicals that damage DNA$
• Genetic predisposition

Definition: Tumors are groups of abnormal cells. They can be benign $non-spreading$ or malignant $capable of spreading and damaging other tissues$.

Highlight: While some cancer risk factors are unavoidable, maintaining a healthy lifestyle and avoiding known carcinogens can help reduce the risk of developing cancer.

The Integumentary System and Skin Functions

The integumentary system consists of the skin, hair, nails, and exocrine glands. Its main functions include:

1. Forming a physical barrier between the external and internal environment
2. Protecting and maintaining body systems
3. Regulating body temperature $thermoregulation$
4. Providing sensory information

Vocabulary: The integumentary system includes the skin and its accessory organs, which work together to protect the body and maintain homeostasis.

Key cell types in the skin include:

• Keratinocytes: Essential for skin repair
• Melanocytes: Responsible for skin pigmentation
• Adipose cells: Store energy in the form of triglycerides
• Langerhans cells: Aid the immune system

The skin plays a crucial role in thermoregulation through various mechanisms:

1. Vasodilation: Widening of blood vessels to release heat
2. Sweating: Production of sweat by sudoriferous $sweat$ glands
3. Piloerection: Contraction of erector pili muscles to generate heat $causing goosebumps$

Example: When you're cold, the erector pili muscles contract, causing your hair to stand up. This creates a layer of insulation and helps retain body heat.

The integumentary system also includes specialized structures like hair follicles, nails, and various glands that contribute to its protective and regulatory functions.

Highlight: The skin is not just a passive barrier; it actively participates in immune defense, temperature regulation, and sensory perception, making it a vital organ for overall health and well-being.

Skin and Immune System Overview

The skin and immune system work together to protect the body from harmful pathogens and maintain health. This overview covers:

• Components of the active and adaptive immune system
• How B lymphocytes function in the immune response
• Ways of preventing disease with healthy diet and vaccines
• Types of infectious diseases and their treatments
• Structure and functions of the skin as part of the integumentary system

Highlight: The immune system has multiple layers of defense, from physical barriers like skin to specialized cells that identify and attack specific pathogens.