Week 24- Introduction , cells, tissues and homeostasis

• The main physiological organ systems of the human body include the Integumentary (skin), Nervous and Endocrine (control of body functions), Circulation/cardiovascular system, Musculoskeletal (provides support and body movement), Respiratory (exchange of gases, oxygen and carbon dioxide), Digestive (nutrient uptake and elimination of waste), Urinary (water balance and excretion), and Reproductive (egg/sperm production).
• The external environment is a cocktail of micro-organisms, some of which are pathogenic.
• Homeostasis is the regulation and maintenance of the internal environment.
• Pathology is the disease or illness, often referred to as pathos, which is suffering.
• Disease internal in origin can be cancer, autoimmunity, inherited disorders (deficiencies of organ systems).
• Disease external in origin can be chemical toxicity, physical injury, invasion by foreign organisms such as HIV, tuberculosis, malarial parasite infections.
• Pathophysiology is the study of bodily functions in a diseased state situation.
• The extracellular matrix consists of a variety of proteins and other molecules, including glycoproteins, actin fibres, and muscle cell membrane.
• Dystrophin mutation leads to loss of mechanical support to the membrane of skeletal muscle cells, causing muscle fibres to rupture and eventually die.
• Dystrophin is a structural protein that links actin to glycoproteins in the extracellular matrix (ECM), providing structural support in muscle cells and stabilizing the plasma membrane of striated muscle cells of skeletal and cardiac muscles.
• “Loss of function” mutations in the genes encoding dystrophin trigger myofibril loss.
• The dystrophin complex acts as an anchor, connecting each muscle cell's structural framework (cytoskeleton) with the lattice of proteins and other molecules outside the cell (extracellular matrix).
• The Extracellular Matrix (ECM) is composed of proteoglycans (a glycoprotein) and insoluble protein fibres such as collagen, fibronectin and laminin, providing strength and anchoring cells in the tissue, particularly in cartilage and bone.
• Tissues with extensive ECM present include epithelial, neural and muscle.
• Plasma in the blood and lymph are very watery but also classed as an extracellular matrix, playing a role in physiological processes such as growth, development and death.
• Cell Junctions are types of Anchoring Junctions found in Tissues such as Adherens Junctions, Desmosomes, Hemidesmosomes, Focal Adhesions, all occurring via proteins called Cadherin Cell Adhesion Molecules (CAMS).
• Adherens junctions link actin fibres of the cytoskeleton together between adjacent cells, using cadherin proteins, making it a cell/cell junction.
• Muscle tissue consists of three types: skeletal, cardiac, and smooth.
• Myelin is a feature of vertebrate animals.
• Transport epithelium is a type of epithelial tissue that selectively moves substances between the lumen and the extracellular fluid.
• Secretory epithelium is a type of epithelial tissue where secretory epithelial cells, such as the cells of the pancreas, make and release products.
• Cytoskeletal filaments in epithelial tissue can be actin or intermediate filaments.
• Neural tissue consists of dendrites, axons, axon myelin, and astrocyte, oligodendrocyte, and neuron cell bodies.
• Basal lamina is a component of epithelial tissue.
• Epithelial tissue allows the exchange of gases like CO2 and O2 in the lungs and the movement of small molecules in and out of blood vessels.
• Myelin is a substance composed of multiple layers of phospholipid membrane that provides support and insulates the axon, speeding up signal transmission.
• Epithelial tissue can be classified into types such as basement membrane, stratified squamous, simple squamous, simple columnar, stratified columnar, polygonal, and simple cuboid.
• Cell junctions are also found in epithelial tissue.
• Ciliated epithelium is a type of epithelial tissue where beating cilia create fluid currents that sweep across the epithelial surface.
• Epithelial tissue can be classified into different types based on its structural features.
• Neurons are the functional units of the nervous system, uniquely shaped with long processes: dendrites receive incoming signals, and axon carries outgoing signal.
• Ivacaftor, a new CFTR potentiator, improves the transport of chloride through the ion channel by binding to the channels directly to induce a non-conventional mode of gating, increasing the probability that the gated chloride ion channel will remain open.
• Cystic Fibrosis (CF) is a multi-system disorder with various clinical features including irreversible lung disease, breathing difficulties, frequent bacterial infection, obstruction of gut, failure to thrive, pancreatic insufficiency, male infertility, and male reproductive tract disorders.
• Treatments for CF patients include physiotherapy to remove mucus from the lungs, antibiotics to treat infection, pancreatic enzymes taken as tablets with food to overcome pancreatic enzyme deficiency due to mucus build up in the pancreas, and new drugs that modify mutant CFTR function or Mucus stickiness.
• Antibiotic-resistant pseudomonas bacteria repeatedly infect the lungs of the CF patient until the infection cant be treated and the patient dies.
• As the mucus becomes more and more viscous over time, it prevents bacteria from being removed from the airway in the lung, and blocks secretion of enzymes from the pancreas.
• Diagnosis of Cystic Fibrosis includes a sweat test, which measures the concentration of chloride ion in sweat, and identification of mutations in the DNA sequence of the CFTR gene.
• The cilia of the epithelial cells normally move trapped pathogens and particles away from the airway towards the pharynx.
• The Cystic Fibrosis transmembrane conductance regulator (CFTR) continues to function poorly in the ciliated epithelium of the airways, clogging the mucociliary escalator.
• Muscular Dystrophy (MD) is a progressive loss of skeletal muscle (muscle wasting) affecting limb movement and respiration due to a mutation, both DMD and BMD versions are inherited as X-linked recessive so only affect boys, most common is Duchenne Muscular Dystrophy (DMD), affecting 1 in 3,000 males, second most common is Becker Muscular Dystrophy (BMD), affecting 1 in 30,000 males, DMD is evident by age 1- 6 years; disease is often fatal by age 25, BMD is milder, onset is later (age 12 or later); affected people live to >50 years.