3 Body and Homeostasis

• Humans have four primary tissue types:

  • Epithelial tissue: covers body surfaces, lines cavities and organs, forms glands
  • Connective tissue: provides support and protection for organs, serves as a storage site for fat, participates in immunity
  • Muscle tissue: responsible for body movement and movement of fluids through the body
  • Nervous tissue: conducts nerve impulses through the body
• All epithelial tissues share two structural characteristics: a free surface and a basement membrane
• Three basic shapes of epithelial cells:

  • Squamous epithelium: flattened cells for diffusion and reducing friction
  • Cuboidal epithelium: cube-shaped cells specialized for secretion and absorption
  • Columnar epithelium: tall, column-shaped cells specialized for secretion and absorption, lines the small intestine
• Epithelial glands:

  • Exocrine gland: secrete into ducts leading to body surfaces, cavities, or organs
  • Endocrine gland: lack ducts and secrete hormones into spaces just outside the cells
• Connective tissue contains cells in an extracellular matrix of protein fibers and ground substance:

  • Protein fibers include collagen, elastic, and reticular fibers
  • Ground substance can be solid (bone), fluid (blood), or gelatinous (cartilage)
• Types of Connective Tissue:

  • Loose connective tissue (areolar connective tissue, adipose tissue): cushions organs and provides insulation
  • Dense connective tissue (in ligaments, tendons, dermis): made of tightly woven fibers
• Specialized connective tissue:

  • Cartilage: tough but flexible, serves as a cushion between bones, heals more slowly than bone
  • Bone: protects and supports internal structures, facilitates movement, stores lipids and minerals, produces blood cells
  • Blood: liquid matrix of plasma, transports various substances
• Skin as an Organ System:

  • Integumentary system composed of skin and its derivatives (hair, nails, sweat glands, oil glands, wax glands)
  • Functions include protection, water loss prevention, temperature regulation, vitamin D synthesis, and stimuli reception
• Skin Damage:

  • Skin color determined by blood flow and melanin distribution
  • Melanin produced by melanocytes, comes in yellow-to-red and black-to-brown forms
• Homeostasis:

  • Constant adjustment by organ systems to respond to internal and external environment changes
  • Maintained through negative feedback mechanisms involving receptors, control center, and effectors
• Thermoregulation involves:

  • Dermal blood vessels and sweat glands
• what are the layers of skin?

  epidermis, dermis, subcutaneous
• What is tight junction?

  • Form a leak-proof seal▪ Found between cells lining the urinary tractand intestines
• What is adhesion junction?


  Hold cells together despite stretching. Found between skin cells
• What is gap junction?


  allow cells communication by allowing small molecules and ions to pass from cell to cell

  Have small holes connecting the cytoplasm ofadjacent cells▪ Found between cardiac muscle cells
• What are the three types of muscle tissue ?

  skeletal, cardiac, smooth
• What are the charactersitics of skeletal muscle tissue?


  voluntary, multi-nucleated, usually attached to skeleton
• What are the main features of smooth muscle tissue?


  involuntary, covering wall of internal organs, non striated spindle shaped and uninucleated
• what are the main features of cardiac muscle tissue?

  fibers: striated, branched and uninucleated, involuntary, only covering walls of heart
• Where does the nervous tissue makes up in the body?

  Brain, spinal cord and nerves 
• What is the function of neurons?

  • Generate nerve impulses and conduct them to other neurons muscle cells or glands 
• What is the function of neuroglia?

  • Support insulate and protect neurons 
• Cells are specialized to perform specific tasks
• Specialized cells are organized into tissues, organs, and organ systems
• Human tissues come in four primary types: epithelial tissue, connective tissue, muscle tissue, and nervous tissue
• Epithelial tissue covers body surfaces, lines body cavities and organs, and forms glands
• Connective tissue serves as a storage site for fat, plays an important role in immunity, and provides the body and its organs with protection and support
• Muscle tissue is responsible for body movement and for movement of substances through the body
• Nervous tissue conducts nerve impulses from one part of the body to another
• Skin is the largest organ in the human body
• Hyaline cartilage provides support and flexibility, found at the ends of long bones and in the nose, ribs, larynx, and trachea
• Elastic cartilage is found in the external ear, providing strength and elasticity
• Fibrocartilage forms a cushioning layer in the knee joint and the outer part of shock-absorbing disks between the vertebrae of the spine
• Bone is a living tissue with functions including protection and support for internal structures, movement, storage of lipids and minerals, and blood cell production
• Blood is a specialized connective tissue consisting of plasma and formed elements like red blood cells, white blood cells, and platelets
• Loose connective tissue contains many cells and functions as a universal packing material between other tissues
• Adipose tissue contains cells specialized for fat storage and serves as long-term energy stores, insulation, and a shock absorber
• Dense connective tissue forms strong bands and is found in ligaments, tendons, and the dermis
• Cartilage serves as cushioning between certain bones and helps maintain the structure of body parts like the ears and nose
• Cartilage:

  • Cells in cartilage (chondrocytes) sit within spaces in the matrix called lacunae
  • Protein fibers and gelatinous ground substance of cartilage provide resilience and strength
  • Cartilage lacks blood vessels and nerves, so nutrients reach cartilage cells by diffusion from nearby capillaries
  • Cartilage heals more slowly than bone due to the slow nutrient diffusion process