Human Physiology PDF

# Human Physiology ## Human Physiology - It is the branch of science that studies the normal functions of human body, cells, organs, and systems. ## The Human Body - The human body consists of cells. - A group of cells from the same type form a primary tissue (muscular, nervous, epithelial and co...

# Human Physiology ## Human Physiology - It is the branch of science that studies the normal functions of human body, cells, organs, and systems. ## The Human Body - The human body consists of cells. - A group of cells from the same type form a primary tissue (muscular, nervous, epithelial and connective tissues). - Two or more primary tissues form an organ (liver, kidneys, heart, etc.) - Different organs perform a related function to form a system (cardiovascular, respiratory, digestive, nervous). ## Cells -> Tissue -> Organ -> Systems ## The Cell - The cell is the basic structural and functional unit of the body. - The cell produces many different functions. - The functions of any organ are the sum of functions of cells composing it. - The cell consist of three principle parts: - Plasma membrane - Cytoplasm and organelles - Nucleus ## Plasma Membrane - The plasma membrane is selectively permeable. - This means that not all molecules can penetrate the cellular membrane. - It allows the entry of molecules according to their size, structure, polarity, and solubility in lipids or water. ## Plasma Membrane (continued) - **Composition:** - **Phospholipids bi-layer:** - It prevents the passage of H₁ and H₁ soluble molecules. - It allows the passage of lipid soluble molecules. - **Proteins:** - They provide structural support, transport H₁ and H₁ soluble molecules and serve as receptors. - **Glycoproteins:** - They have diverse functions such as in immune system (blood group determination), protection of the body (mucus secretion), and communication between cells. ## Cytoplasm, Organelles, Nucleoli - **Cytoplasm:** - It is the aqueous content of the cell. - **Organelles:** - They are sub-cellular structures within the cytoplasm. - **Nucleus:** - It is a large spheroid body. - It is the largest organelle within the cell. - It contains genetic material (DNA). - **Nucleoli:** - They are the centers for production of ribosomes. ## Cytoplasm, Organelles, Nucleoli (continued) - **Cytoplasm:** - It is a jelly-like matrix within the cell where cell organelles are suspended. - It contains a highly organized structure with microtubules and microfilaments (mainly Actin that functions as cytoskeleton). ## Lysosomes - Lysosomes are responsible for: - **Digestion:** - Because they contain digestive enzymes for digestion of nutrient,s and harmful molecules. - **Autophagy:** - It is the process that destroys worn-out (old) organelles, so that they can be continuously replaced. - **Apoptosis (Programmed cell death):** - Lysosomes release digestive enzymes into the cell so, a naturally programmed cell death is started that is called apoptosis. ## Mitochondria - Mitochondria are the sites for energy production (ATP molecules production) of all cells (except, in mature RBCs). - They contain their own DNA and can reproduce themselves. ## Ribosomes - Ribosomes are essential for protein synthesis in the cell. - Proteins produced according to genetic information contained in mRNA. - Ribosomes are located both in the cytoplasm and on the surface of endoplasmic reticulum. ## Endoplasmic Reticulum (ER) - ER is two types: - **Granular (rough) ER:** - It carries ribosomes on its surface, in cells active in protein synthesis. - Proteins enter ER are modified for secretion. - **A granular (smooth) ER:** - It provides a site for steroid hormone production and inactivation. - Storage of Ca²⁺ (calcium) ions. ## Golgi Complex - It is hollow, flattened sacks-like organelle with cisternae. - It modifies proteins and separates them according to their final destination. ## Cell Nucleus - Most cells have a single nucleus. - Some cells such as Red Blood Cells (RBCs) contain no nucleus. - Enclosed by inner and outer membrane called the nuclear envelope. - **Functions of the nucleus:** - It contains the genetic material (DNA). - It controls all cellular functions by regulating gene expression. ## Chromosomes - They are found in the nucleus. - They made of DNA. - They contain instructions for characteristics. - **Somatic cells** contain 46 chromosomes. - **Germ cells** (sperms and ova) contain 23 chromosomes. ## Nucleolus - It constitutes 25% of the nuclear volume. - It composed of proteins and RNA. - It is the center for production of ribosomes.