Human Body Systems

Anatomy vs. Physiology

  • Anatomy: Study of the structure of an organism’s body parts (form).
  • Physiology: Study of the functions of those parts.

Fun Facts – Body Edition

  • Largest organ: Skin (16% of body).
  • Longest bone: Femur (thigh bone).
  • Smallest bone: Stapes (“stirrup”—in ear).
  • Absent bone in humans (present in most other primates/mammals): Baculum (penis bone).

Tissues

  • Cells work cooperatively as a tissue to perform a specific function.
  • Animal bodies contain these tissue types:
    • Epithelial tissue.
    • Connective tissue.
    • Muscle tissue.
    • Nerve tissue.

Epithelial Tissue (Epithelium)

  • Primary functions:
    • Protection (barrier between inside and outside of the body).
    • Secretion (glands secrete saliva, sweat, mucous, stomach acid, digestive enzymes, and hormones).
  • Location: Whole surface of the body, including the lining of the digestive tract.

Connective Tissue

  • Binds to and supports other tissues.
  • Cells are scattered inside non-cellular material (fluid, mineral, etc.).
  • Examples: Bone, cartilage, adipose (fat), blood.

Nerve Tissue

  • Location: Brain, spinal cord, and scattered throughout the body.
  • Primary function: Communicates signals between the brain and the rest of the body.

Muscle Tissue

  • General appearance: Bundles of long cells called muscle fibers.
  • General function: Fibers contain specialized proteins that allow it to contract.
  • Locations and type of control:
    • Smooth muscle: Blood vessels and the digestive tract (involuntary).
    • Cardiac muscle: Heart tissue (involuntary).
    • Skeletal muscle: Attaches to bones (voluntary).

Homeostasis

  • Animal bodies maintain relatively constant internal conditions.
  • When the external environment changes drastically, the body uses various mechanisms to maintain internal systems.

Detecting and Responding to Changes in the Environment

  • Negative feedback (most common): The results of a process inhibit that very process.
    • Example: Body temperature.
      • Stimulus: hot weather → body temp rises.
      • Response: produce sweat.
      • Result: temp returns to normal.
      • Stimulus: cold weather → body temp falls.
      • Response: goose bumps (raise body hairs to trap warmth).
      • Result: temp returns to normal.

Body Temperature Regulation

Ectotherms
  • Get their heat from the environment.
  • Sometimes called “cold-blooded”.
  • Examples: Invertebrates, fishes, amphibians, and reptiles.
Endotherms
  • Generate body heat internally.
  • Sometimes called “warm-blooded”.
  • Examples: Mammals and birds.

Four Primary Mechanisms for Regulating Body Temperature

  • Physical (anatomical).
  • Behavioral.
  • Physiological.
  • Cellular.
Examples of Ways to Regulate Body Temp
  • Physical Methods:
    • The walrus has a thick coat of blubber that provides insulation from the external environment.
  • Behavioral Methods:
    • The African ground squirrel shades itself with its tail while foraging, to minimize heat from the sun.
  • Physiological Methods:
    • By panting, dingos make use of the efficient loss of heat due to evaporation.
  • Cellular Methods:
    • Human infants have a special type of fat that produces heat, rather than ATP, when broken down.

Diabetes

  • An example of a breakdown in homeostasis.
  • The body fails to produce enough insulin (type 1) or target cells do not respond normally (type 2).
  • Causes:
    • Genetic.
    • Environmental.
  • Results:
    • Liver/kidney damage.
    • Blindness.
    • Amputations.
    • Significant contributor to 25% of deaths.

Positive Feedback

  • A form of regulation in which the results of a process intensify that same process.
  • Example: Childbirth.
    • Hormones stimulate uterine contractions.
    • Contractions stimulate the release of more hormones.
    • Result: more contractions.

The Digestive System

  • A continuous tube that runs from the mouth to the anus
  • Tube is called the Alimentary Canal

Alimentary Canal

  • The mouth, also called the oral cavity, is the site of ingestion.
  • The section at the back of the mouth is called the pharynx
  • The pharynx splits into two tubes
    • Esophagus: leads to the gut.
    • Trachea leads to the lungs.
  • The epiglottis moves to cover the entrance to the trachea, directing food down the esophagus.

Food Processing – Four Stages

  • Ingestion (eating).
  • Digestion (mechanical and chemical).
  • Absorption (primarily by cells lining the small intestine).
  • Elimination.
Digestion
  • Mechanical digestion (mostly chewing) is the use of physical processes to break down food into smaller pieces.
  • Chemical digestion is the use of enzymes to perform hydrolysis, chemical reactions that use water to break bonds within large molecules.

Chemical Digestion

  • Occurs in the mouth, stomach and intestines
  • Food moves through the gut through contractions called peristalsis.
  • Cells lining the stomach secrete gastric juice, containing enzymes (such as pepsin) and acids.
  • Sphincter muscles closes the stomach after food enters, preventing back-flow of stomach acids into the esophagus.
  • Another sphincter closes the stomach from the small intestine.
  • Food particles are called "Chyme"
Gastric Bypass Surgery
  • Surgery makes the stomach smaller.
  • Food "bypasses" most of the stomach and part of the small intestine

Chemical Digestion in the Small Intestine

  • The small intestine is all about maximizing surface area for absorption of nutrients:
    • Length, villi, and microvilli
  • SMALL INTESTINE
    • 20 feet long with many folds
  • VILLI
    • Finger-like projections that line the small intestine
  • MICROVILLI
    • Thread-like projections that line cells in the villi
  • The surface area of the small intestine is equivalent to a TENNIS COURT!

Digestion Completion

  • Digestion is completed in the small intestine, at which point carbohydrates, proteins, and fats have been broken down into simple sugars, amino acids, and fatty acids.

Colon (large intestine)

  • The remaining chyme—mostly indigestible materials—leaves the small intestine and enters the large intestine, or colon.
  • Water, salts, and some vitamins are absorbed.
  • The colon ends in a chamber called the rectum.
    • A storage compartment for the feces (mostly, indigestible parts of consumed food).
  • Symbiotic bacteria produce vitamins and aid in digestion

Diseases that effect the intestines

  • Celiac and Chron’s Disease– autoimmune disease that effects the intestines

Accessory Organs

  • Accessory organs secrete specific digestive chemicals into the alimentary canal via ducts.
    • Salivary glands: Secrete enzymes that break down starch (a carbohydrate).
    • Liver: Secretes bile for breaking up fats.
    • Gall bladder: Stores bile.
    • Pancreas: Secretes lots of digestive enzymes.

Illnesses of the Digestive System

  • Common ailments include:
    • Acid reflux
    • Gallstones
    • Constipation
    • Appendicitis
    • Cholera
    • Inflammatory bowel disease
    • Ulcer

Food For Thought

  • Is it possible for a person to be both obese and malnourished