Animal Bodies and Homeostasis Notes

Chapter 41 Animal Bodies and Homeostasis

Key Concepts

• Organization of Animal Bodies:
  • Cells with similar properties group to form tissues.
  • Tissues combine to form organs.
  • Organs are linked to form organ systems.
• General Principles of Homeostasis

Organization of Animal Bodies

• All animal cells share similarities:
  • Exchange materials with their surroundings.
  • Obtain energy from organic nutrients.
  • Synthesize complex molecules.
  • Reproduce themselves.
  • Detect and respond to signals in their immediate environment.
• Animals begin life as a single cell (fertilized egg) that divides multiple times.
• Daughter cells become specialized to perform particular functions.

Internal Organization of Animals

• Cells with similar properties group to form tissues.
• Tissues combine to form organs.
• Organs are linked to form organ systems.
• Example:
  • Differentiated cell types in monkeys include muscle cells, neurons, epithelial cells, and connective cells.
  • These cells make up muscle tissue, nervous tissue, epithelial tissue, and connective tissue, respectively.
  • These tissues come together in an organ called the urinary bladder, which is part of the urinary system.
  • The urinary system is an organ system composed of the kidneys, ureter, bladder, and urethra.

Tissues

• Tissue is an association of many cells that have a similar structure and function.
• Four tissue types in animals:
  • Muscle Tissue: Cells specialized to shorten/contract, generating mechanical force.
  • Nervous Tissue: Complex networks of cells called neurons.
  • Epithelial Tissue: Sheets of densely packed cells with various functions.
  • Connective Tissue: Connect, surround, anchor, and support structures of an animal’s body.

Muscle Tissue

• Muscle cells are specialized to contract, generating mechanical force.
• Three types of muscle tissue:
  • Skeletal Muscle:
    • Attached to the skeleton for locomotion.
    • Under voluntary control.
  • Smooth Muscle:
    • Surrounds tubes and cavities for propulsion of contents.
    • Under involuntary control.
  • Cardiac Muscle:
    • Only in the heart.
    • Under involuntary control.
• Skeletal muscles are usually attached to bone in vertebrates and provide the force needed for locomotion. All muscle skeletal is under voluntary control
• Smooth muscles often surround hollow tubes and control the tube’s diameter. Smooth muscle contraction is involuntary.
• Cardiac muscle is found only in the heart, where muscle cells are interconnected and provide the force needed for a heartbeat. Cardiac muscle contraction is involuntary.
• Bronchioles
  • Smooth muscle controls the degree to which tubes are opened
  • In asthma, smooth muscle tissue in air tubes called bronchioles is sometimes in a highly contracted state.

Nervous Tissue

• Complex networks of neurons.
• Neurons are cells that initiate and conduct electrical signals from one part of the animal’s body to another.
• Electrical signals produced in one neuron may stimulate or inhibit other neurons to:
  • Initiate new electrical signals.
  • Stimulate muscle cells to contract.
  • Stimulate glandular cells to release chemicals.

Epithelial Tissue

• Sheets of densely-packed cells.
• Different kinds are named and defined based on:
  • Shapes of cells.
  • Number of cell layers.
  • Characteristics of the cell layers.
• Functions:
  • Cover the body.
  • Enclose organs.
  • Line the walls of body cavities.
• Specialized to protect and to secrete and absorb ions and organic molecules.
• Epithelial cells have a variety of shapes:
  • Cuboidal: cube-shaped.
  • Squamous: flat and scale-like.
  • Columnar: shaped like a column.
• Epithelial cells are arranged to form different types of tissues:
  • Simple – one layer.
  • Stratified – multiple layers.
  • Pseudostratified – one layer, but appears stratified.
  • Transitional – multiple layers; can expand and contract.
• Examples:
  • Simple cuboidal tissue has one layer of cube-shaped cells.
  • Stratified cuboidal tissue has multiple layers of cube-shaped cells.
  • Simple squamous tissue has one layer of squamous cells.
• Asymmetrical (polarized):
  • One side rests on basal lamina and the other faces environment.
  • Can function as selective barriers.
• Examples of epithelial tissues:
  • Nasal passages: Pseudostratified ciliated columnar.
  • Kidney tubules: Simple cuboidal.
  • Esophagus lining: Stratified squamous.
  • Lungs: Simple squamous.
  • Urinary system: Transitional.
  • Intestines: Simple columnar.
• The lungs of animals are lined with a single layer of flat cells, called simple squamous tissue.
• Intestines are lined with a single layer of tall cells, called simple columnar tissue.
• The urinary system is lined with stacked stratified cells called transitional tissue.
• The kidneys are lined with a single layer of cells, called simple cuboidal tissue.
• In the esophagus, flat cells are stacked on top of one another, called stratified squamous tissue.
• In nasal passages, tall and short cells are side by side giving the tissue the appearance of being stratified, called pseudostratified ciliated columnar tissue.

Connective Tissue

• Connect, surround, anchor, and support.
• Includes: blood, adipose, bone, cartilage, loose and dense connective tissue.
• Cells of connective tissues form extracellular matrix (ECM) around cells.
  • Provides scaffold for attachment.
  • Protects and cushions.
  • Mechanical strength.
  • Transmit information.
• Proteins of the ECM consist of two types:
  • Collagen and elastin (fibers).
  • Adhesive proteins.
• Blood: composed of red and white blood cells and platelets suspended in plasma rich in electrolytes, proteins, and other solutes.
• Adipose tissue: composed of lipid-filled cells, providing protection and insulation around internal organs and under the skin; also a major energy store.
• Bone: composed of bone-forming cells that secrete collagen embedded in a hard casing of calcium and phosphorus, providing inflexible, tough characteristics for support and protection.
• Cartilage: formed by collagen-secreting cells, not mineralized, softer and more flexible than bone, providing flexibility of movement and cushioning of joints in animals with bony skeletons.
• Loose connective tissue: abundant throughout animals' bodies, holding internal organs in place and providing much of the internal framework of the body; composed of loosely arranged collagen fibers mixed with elastin.
• Dense connective tissue: as in tendons and ligaments, has tightly packed layers of collagen fibers in parallel arrays, giving the tissue great strength but very little flexibility.
• Mammalian connective tissue can be isolated cells, like blood that transports materials throughout the body, clumps of cell, like fat that provides a layer of protection and insulation around vulnerable internal organs in addition to acting as an energy source, or as rigid material like bone and cartilage that support and protect the body while allowing for complex movements.
• Loose connective tissue is abundant throughout animals’ bodies, where it holds internal organs in place and provides much of the internal framework of the body. It is composed of loosely arranged collagen fibers mixed with elastin fibers, which allows it to be flexible.
• Dense connective tissue, as in tendons and ligaments, has tightly packed layers of collagen fibers in parallel arrays, giving the tissue great strength but very little flexibility.

Organs and Organ Systems

• Organs: Composed of two or more kinds of tissues; may form sheets, tubes, layers, bundles, or strips.
• Organ system: Different organs work together to perform an overall function, e.g., the stomach is an organ that is part of the digestive system.
• Organ systems frequently work together, e.g., the nervous, circulatory, and endocrine systems function together to influence how much water the kidney retains.
• The vertebrate stomach is composed of all four tissue types: epithelial, connective, nervous, and muscle.
• The lumen of the stomach is lined with simple columnar epithelial tissue. Below this layer is connective tissue. Small arteries and veins are found within the connective tissues. Below this are layers of smooth muscle tissue with nervous tissue in between. Below the smooth muscle tissue is more connective tissue, and finally simple squamous epithelial tissue.

Organ Systems Found in Animals

The Relationship Between Structure and Function

• Compare respiratory systems of insects and mammals:
  • Similar structure suggests similar function.
  • Tubes connect with the outside environment terminating in single-cell thick structures.
  • Tubes serve as air conduits.
  • Thin cells with high surface area for diffusion of gases.
• In insects, respiration is achieved via a series of smaller and smaller tubes, called trachea and tracheoles, that are connected to the external environment on one end and directly to muscle tissues on the other end.
• In mammals, respiration occurs across the thin surfaces of the alveoli which are at the terminal ends of series of smaller and smaller branches of tubes in the lungs that are connected to the external environment on one end and oxygen carried to muscle tissues via blood at the other end.