Cell Structure and Function

Cell Structure

• The cell is the smallest living unit in the body.
• The plasma membrane acts as a selective barrier, regulating the transport of substances in and out of the cell. It is made up of a phospholipid bilayer and proteins.
• Cytoplasm is a jelly-like fluid filling the cell's interior.
• Organelles are specialized parts of cells performing unique functions.
• The nucleus contains DNA and RNA, storing genetic code.
• Mitochondria are the "power plants" of cells, producing ATP.
• The endoplasmic reticulum is a network of membranes transporting materials. Smooth ER is free of ribosomes, while rough ER has ribosomes on its surface.
• Ribosomes are "protein factories," producing proteins.
• The Golgi apparatus packages and transports newly created protein compounds.
• Lysosomes are the "garbage collectors," removing damaged or worn-out cell parts.
• The cytoskeleton helps maintain the cell's shape, including microtubules and microfilaments. The centrosomes form the mitotic spindle, crucial during cell division

Tissues

• Tissues are collections of similar specialized cells.
• Epithelial tissues cover and line external and internal body surfaces, including small cavities. Stratified tissues are layered, and squamous cells are flattened.
• Connective tissues include fibroblasts, which produce protein fibers like collagen, a crucial component of many connective tissues, found in most tissues except blood. Loose connective tissue is found in the oral mucosa, cartilage is firm, bone is rigid, and blood is fluid.
• Cartilage has two types: chondroblasts (immature cells that produce the cartilage matrix) and chondrocytes (mature cells that maintain the cartilage matrix).
• Bone tissue forms the skeletal system. Osteoblasts form bone, osteocytes maintain mature bone, and osteoclasts break down bone. Two types of bone are compact (strong, few spaces) and spongy (lattice with soft tissue spaces).
• Blood connects all body systems, transporting oxygen, nutrients, and waste. Red blood cells (RBCs) contain hemoglobin for oxygen transport, white blood cells (WBCs) act as the first line of defense against injury and disease, and platelets play a role in clotting.