Cell Specialization and Differentiation

Cell Specialization

• Cells specialize to perform specific functions for efficiency in multicellular organisms.
• Red blood cells specialize in carrying oxygen.
• Muscle cells specialize in contraction for movement.
• Nerve cells specialize in transmitting electrical impulses.
• Epithelial cells specialize in protecting surfaces and lining organs.

Stem Cells and Cellular Differentiation

• Stem cells are undifferentiated cells that can divide and specialize into various cell types.
• Embryonic stem cells are pluripotent and can become any cell type in the body.
• Adult stem cells are multipotent and can become a limited number of cell types.
• Induced pluripotent stem cells (iPSCs) are reprogrammed adult cells that behave like embryonic stem cells.
• Cellular differentiation is the process by which a stem cell develops into a specialized cell.
• Differentiation is influenced by genetic information, chemical signals, and environmental factors.
• Self-renewal of stem cells allows them to maintain the stem cell population.

Levels of Organization in an Animal (Hierarchy)

• Cells are the basic structural and functional units of life.
• Tissues are groups of similar cells performing a common function which organize cells into functional structures.
• Organs are structures composed of different tissues working together.
• Organ systems are groups of organs working together for a broader function.
• An organism is an individual made up of organ systems working in harmony.

Four Major Types of Tissues

• Epithelial tissue has tightly packed cells forming layers for protection, absorption, secretion, and filtration and examples are skin and the lining of the digestive tract.
• Connective tissue has cells embedded in an extracellular matrix; it supports, connects, stores nutrients, and protects, and examples are bone, blood, cartilage, and adipose tissue.
• Muscle tissue contains contractile proteins (actin and myosin) for movement.
  • Skeletal muscle is voluntary, striated, and moves bones.
  • Cardiac muscle is involuntary, striated, and found in the heart.
  • Smooth muscle is involuntary, non-striated, and found in internal organs.
• Nerve tissue contains neurons and glial cells for transmitting electrical impulses to coordinate body functions, and an example is the brain, spinal cord, and peripheral nerves.

Primary Structures and Functions of the Following Organ Systems

• Digestive System: organs include the mouth, esophagus, stomach, small intestine, large intestine, liver, and pancreas and its function is to break down food, absorbs nutrients, and eliminate waste.
  • Digestion begins in the mouth and nutrients are mostly digested by the duodenum.
  • Mechanical digestion involves chewing and stomach churning.
• Chemical digestion involves enzyme activity.
• Nutrients are absorbed in the small intestine
• The liver produces bile and processes nutrients.
• Bile from the gallbladder helps dissolve fats.
• The pancreas produces digestive enzymes and regulates blood sugar.
• The large intestine absorbs water and salts, preparing waste for elimination.
• Feces are stored in the rectum.
• Feces are eliminated from the body through the anus.
• Circulatory System: organs include the heart, blood vessels (arteries, veins, capillaries), and blood and its function is to transport of oxygen, nutrients, and waste products.
• Blood vessels carry blood to and from organs.
• Blood carries gases, nutrients, and waste.
• The heart consists of four chambers: the right atrium, right ventricle, left atrium, and left ventricle.
  • The superior vena cava carries deoxygenated blood from the upper body to the right atrium.
  • Deoxygenated blood returns to the right atrium through the superior and inferior vena cava.
  • The right ventricle pumps deoxygenated blood to the lungs via the pulmonary artery.
  • The lungs oxygenate the blood.
  • Oxygenated blood returns to the left atrium via the pulmonary veins.
  • The left ventricle pumps oxygenated blood to the entire body.
  • The aorta is the largest artery for carrying oxygenated blood to the body.
  • Arteries branch into arterioles, leading to capillaries.
  • Capillaries are where oxygen, nutrients, and waste are exchanged with tissues.
  • Deoxygenated blood collects in venules, which converge into veins and blockage of arteries are opened by expansion.
  • Veins carry deoxygenated blood back to the heart via the vena cava.
• Circulatory Path: Right Atrium → Right Ventricle → Pulmonary Artery → Lungs → Pulmonary Veins → Left Atrium → Left Ventricle → Aorta → Arteries → Capillaries → Venules → Veins → Superior/Inferior Vena Cava → Right Atrium.
• Respiratory System: organs include the nose, trachea, bronchi, lungs, and diaphragm and its function is gas exchange (oxygen in, carbon dioxide out).
  • The nose filters, moistens, and warms incoming air.
  • Air travels through the pharynx to the larynx, then to the trachea.
  • The trachea divides into bronchi, entering the lungs.
  • Bronchi divide into bronchioles, ending in alveoli.
  • Gas exchange occurs in the alveoli.
  • Inhalation brings oxygen into the lungs.
  • Exhalation expels carbon dioxide.
• Respiratory Path: Nose/Mouth → Nasal Passages/Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli → Gas Exchange → Exhalation.

Liver

• The liver detoxifies and metabolizes substances.
• It also processes nutrients, stores glycogen, produces bile, and regulates blood sugar levels.

Pancreas

• The pancreas regulates blood sugar and aids digestion.
• It produces insulin and glucagon to regulate blood sugar levels.
• Also produces digestive enzymes that help break down food in the small intestine.

Interaction of Systems

• Organ systems work together to maintain homeostasis and perform complex functions.
• The circulatory system transports oxygen from the lungs to tissues, while the respiratory system brings in oxygen and expels carbon dioxide.
• The nervous system sends signals to muscles for movement.
• Nutrients from digested food are absorbed into the bloodstream and delivered to cells.
• Hormones released from glands are transported through the bloodstream to target organs.

Organ Transplantation (Issues, Risks, and Benefits)

• Living Donors: A living person donates an organ.
• Benefits: Shorter waiting times, better outcomes.
• Risks: Surgical complications, potential organ rejection, emotional and physical risks for the donor.
• Deceased Donors: Organs are harvested from individuals declared brain-dead.
• Benefits: Larger pool of potential organ donors.
• Risks: Organ rejection, limited availability of organs, ethical concerns about organ procurement.
• Xenotransplantation: Transplantation of animal organs into humans and this could alleviate organ shortages.
• Risks involved are potential for disease transmission, organ rejection, ethical concerns about using animals for organ harvesting.