🤾🏻‍♂️Human Physiology Engineering Unit 3 – Tissues & Organ Systems in Human Physiology

Key Concepts

• Tissues are groups of cells with similar structure and function that work together to perform specific roles in the body
• The four main types of tissues in the human body include epithelial, connective, muscle, and nervous tissue
• Organs are composed of multiple tissue types that work together to carry out complex functions
• Organ systems consist of multiple organs that collaborate to perform specific physiological processes (digestion, respiration, circulation)
• Homeostasis maintains stable internal conditions in the body through various regulatory mechanisms
  • Involves feedback loops (negative feedback, positive feedback) to adjust physiological parameters
• Tissue engineering applies principles of biology and engineering to develop functional tissue substitutes for medical applications
• Histology is the study of tissues at the microscopic level using various staining and imaging techniques

Types of Tissues

• Epithelial tissue covers body surfaces, lines cavities, and forms glands
  • Classified based on cell shape (squamous, cuboidal, columnar) and number of layers (simple, stratified)
• Connective tissue supports, protects, and binds other tissues
  • Includes loose connective tissue (adipose), dense connective tissue (tendons, ligaments), and specialized connective tissue (cartilage, bone, blood)
• Muscle tissue enables movement and generates force
  • Classified into skeletal muscle, smooth muscle, and cardiac muscle based on structure and function
• Nervous tissue transmits electrical signals and processes information
  • Composed of neurons (nerve cells) and glial cells that support and protect neurons
• Stem cells are unspecialized cells capable of differentiating into various tissue types
  • Play a crucial role in tissue repair, regeneration, and engineering applications

Tissue Structure and Function

• Epithelial tissue functions include protection, secretion, absorption, and filtration
  • Tight junctions between epithelial cells create a selective barrier and maintain tissue integrity
• Connective tissue provides structural support, cushioning, and energy storage
  • Extracellular matrix (ECM) is a key component of connective tissue, consisting of fibers (collagen, elastic) and ground substance
• Muscle tissue generates force through contraction, enabling movement and maintaining posture
  • Sarcomeres are the basic functional units of muscle fibers, containing myosin and actin filaments
• Nervous tissue enables rapid communication and information processing
  • Neurons transmit electrical signals called action potentials along their axons
  • Synapses are specialized junctions that allow neurons to communicate with each other or with target cells
• Tissue structure is closely related to its function, with specific cell types and arrangements optimized for their roles

Major Organ Systems

• Integumentary system (skin, hair, nails) provides a protective barrier, regulates body temperature, and enables sensory perception
• Skeletal system (bones, cartilage, ligaments) provides structural support, protects internal organs, and enables movement
• Muscular system (skeletal, smooth, cardiac muscle) generates force for movement, maintains posture, and supports cardiovascular function
• Nervous system (brain, spinal cord, nerves) processes information, coordinates body functions, and enables communication between the body and the environment
• Endocrine system (glands, hormones) regulates growth, development, metabolism, and homeostasis through chemical signaling
• Cardiovascular system (heart, blood vessels, blood) transports oxygen, nutrients, and waste products throughout the body
• Lymphatic system (lymph nodes, vessels, tissues) maintains fluid balance, facilitates immune responses, and absorbs fats from the digestive system
• Respiratory system (lungs, airways) enables gas exchange between the body and the environment

Tissue-Organ Relationships

• Organs are composed of multiple tissue types that work together to perform specific functions
  • For example, the heart contains cardiac muscle tissue for contraction, connective tissue for structural support, and epithelial tissue lining the chambers and valves
• Tissue arrangement and interaction within organs are crucial for proper organ function
  • In the small intestine, epithelial tissue forms villi and microvilli to increase surface area for absorption, while smooth muscle tissue enables peristalsis for food movement
• Tissue damage or dysfunction can lead to organ-level impairments and systemic effects
  • Fibrosis, or excessive connective tissue formation, can disrupt normal organ structure and function (cirrhosis in the liver, pulmonary fibrosis in the lungs)
• Understanding tissue-organ relationships is essential for diagnosing and treating diseases, as well as for developing targeted therapies and regenerative medicine approaches

Homeostasis and Regulation

• Homeostasis is the maintenance of stable internal conditions in the face of external changes
  • Involves monitoring physiological parameters (body temperature, blood glucose, pH) and adjusting them as needed
• Negative feedback loops are the primary mechanism for maintaining homeostasis
  • Deviations from the set point trigger compensatory responses to restore balance (thermoregulation, blood pressure control)
• Positive feedback loops amplify changes and are less common in physiological processes
  • Examples include blood clotting cascade and uterine contractions during childbirth
• Hormones and the autonomic nervous system play key roles in regulating homeostasis
  • Endocrine glands secrete hormones that act on target tissues to modulate their function (insulin regulates blood glucose)
  • The sympathetic and parasympathetic divisions of the autonomic nervous system have opposing effects on various organs to maintain balance

Clinical Applications

• Tissue engineering combines principles of biology, materials science, and engineering to create functional tissue substitutes
  • Involves scaffolds, cells, and bioactive molecules to guide tissue regeneration
  • Applications include skin grafts for burn victims, cartilage repair for joint injuries, and blood vessel replacements
• Regenerative medicine aims to restore or replace damaged tissues and organs using stem cells, growth factors, and biomaterials
  • Induced pluripotent stem cells (iPSCs) are derived from adult cells and can differentiate into various tissue types
• Tissue and organ transplantation are used to replace failing or damaged tissues
  • Requires careful matching of donor and recipient to minimize immune rejection
  • Tissue banking and cryopreservation enable long-term storage and on-demand use of tissues for transplantation
• Personalized medicine tailors treatments based on an individual's genetic profile, tissue characteristics, and disease state
  • Tissue-based diagnostics (biopsies, molecular profiling) guide treatment decisions and monitor therapeutic responses

Lab Techniques and Tools

• Histology involves the microscopic study of tissue structure and organization
  • Tissue samples are fixed, sectioned, and stained with dyes (hematoxylin and eosin) to visualize cell and tissue components
• Immunohistochemistry uses antibodies to detect specific proteins in tissue sections
  • Enables the identification and localization of cell types, disease markers, and signaling molecules
• Tissue culture techniques allow the growth and maintenance of cells and tissues outside the body
  • Primary cell cultures are derived directly from tissues, while cell lines are immortalized and can be passaged indefinitely
• Microscopy is essential for visualizing and analyzing tissues at various scales
  • Light microscopy (bright-field, phase-contrast) is used for routine histological examination
  • Electron microscopy (scanning, transmission) provides higher resolution for ultrastructural analysis
  • Confocal microscopy enables 3D imaging and visualization of fluorescently labeled structures
• Tissue engineering scaffolds are designed to mimic the natural extracellular matrix and support cell growth and differentiation
  • Materials include polymers (collagen, hyaluronic acid), ceramics (hydroxyapatite), and metals (titanium)
  • 3D printing and electrospinning techniques enable the fabrication of complex scaffold architectures