Study sheet: Mechanisms of Disease

📋 Course Outline

1. Basic Cell Structure and Organelles
2. Cell Membrane and Its Proteins
3. Transport Across the Cell Membrane
4. Cellular Adaptation to Stress
5. Benign and Malignant Neoplasia
6. Cancer Manifestations and Cachexia

📖 1. Basic Cell Structure and Organelles

🔑 Key Concepts & Definitions

• Cell : The basic structural and functional unit of the body, consisting of a cell membrane, cytoplasm, nucleus, and major organelles.

★ Must-know

• The major cell organelles are:
  • mitochondria
  • ribosomes
  • endoplasmic reticulum
  • Golgi apparatus
  • lysosomes

Further detail

• The nucleus is a major cell component, while the cytoplasm occupies the region between the nucleus and cell membrane.

📖 2. Cell Membrane and Its Proteins

🔑 Key Concepts & Definitions

• Cell Membrane : A very thin, flexible structure that encloses each cell, supports its internal structure, and selectively controls the entry and exit of substances.

★ Must-know

📌 Integral proteins are embedded within the lipid bilayer, whereas peripheral proteins are attached to the membrane surface without penetrating it.

• Membrane channels selectively allow water-soluble substances such as sodium and potassium ions to pass through the membrane.

Further detail

• Carrier proteins change shape to transfer substances that cannot cross the cell membrane independently.

• Membrane receptors are located on the outer surface and each receptor is specific for a certain molecule.

📖 3. Transport Across the Cell Membrane

🔑 Key Concepts & Definitions

• Simple Diffusion : The movement of molecules across the cell membrane according to their concentration gradient without energy or a carrier protein.
• Osmosis : The diffusion of water from a solution with lower solute concentration to a solution with higher solute concentration.
• Facilitated Diffusion : Facilitated diffusion is passive movement of molecules down their concentration gradient through a carrier protein without energy, as occurs with glucose and amino acids.

★ Must-know

• Passive transport moves molecules down their concentration gradient without energy, whereas active transport moves molecules against their concentration gradient and requires energy.

• Intravenous solutions must be isotonic and iso-osmotic.

• Endocytosis brings large particles into the cell using energy, whereas exocytosis releases secretory products from the cell using energy.

Further detail

• Pinocytosis ingests small vesicles containing extracellular fluid and large molecules such as proteins, whereas phagocytosis engulfs large particles such as bacteria or dead tissue.

💡 Memory Hook

Passive follows the gradient; active opposes it; vesicular transport moves large particles.

📖 4. Cellular Adaptation to Stress

🔑 Key Concepts & Definitions

• Hypertrophy : Hypertrophy is an increase in cell size, as seen in skeletal muscle with exercise and cardiac hypertrophy in hypertension.
• Hyperplasia : Hyperplasia is an increase in cell number and may occur through hormonal stimulation.
• Atrophy : Atrophy is a decrease in cell size caused by factors such as disuse, poor nutrition, or aging.
• Metaplasia : The replacement of one mature cell type by another mature cell type that is better able to tolerate stress.

★ Must-know

• When a cell experiences stress or a stimulus, it may adapt and thereby survive.

Further detail

• Chronic smoking can cause changes in the respiratory epithelium through metaplasia.

💡 Memory Hook

Stress → adaptation → survival.

📖 5. Benign and Malignant Neoplasia

🔑 Key Concepts & Definitions

• Neoplasia : Abnormal, uncontrolled proliferation of cells that may produce benign or malignant tumors.

📝 Essential Points

• Benign tumors usually:

  • grow slowly
  • closely resemble their tissue of origin
  • do not invade surrounding tissues
  • cause minimal or absent tissue destruction
  • do not metastasize
  • may be encapsulated

• Malignant tumors usually: grow rapidly or uncontrollably, may show little resemblance to their tissue of origin, invade surrounding tissues, cause tissue destruction, may metastasize to distant sites, are usually not encapsulated

💡 Memory Hook

Benign tumors remain localized, whereas malignant tumors invade and may metastasize.

📖 6. Cancer Manifestations and Cachexia

🔑 Key Concepts & Definitions

• Cachexia : A complex syndrome characterized by anorexia, weight loss, and muscle wasting.

★ Must-know

• Local effects of cancer include:

  • compression of blood vessels
  • obstruction of hollow organs
  • ischemia
  • pain
  • bleeding
  • infection
  • altered tissue function

• Systemic effects of cancer include:

  • fatigue
  • cachexia
  • bleeding and hemorrhage
  • fever
  • anemia
  • altered organ function
  • abnormal hormone production

Further detail

• Cachexia is more common in children and elderly persons and becomes more pronounced as the disease progresses.

💡 Memory Hook

Cancer causes local and systemic effects → cachexia with anorexia, weight loss, and muscle wasting.

📊 Synthesis Tables

Benign and Malignant Tumors

Feature	Benign tumors	Malignant tumors
Growth rate	Usually slow-growing	Usually rapid or uncontrolled growth
Resemblance to tissue of origin	Usually closely similar	May show little resemblance
Local invasion	Usually absent	Invade surrounding tissues
Tissue destruction	Minimal or absent	Often causes tissue destruction
Metastasis	Do not metastasize	May metastasize to distant sites
Capsule	May be encapsulated	Usually not encapsulated