Human Body Systems - Module 7

Human Body Systems

Organization of the Body

• The human body is made up of cells, tissues, organs, and organ systems that work together to maintain homeostasis.
• The levels of organization in a multicellular organism include:
  • Cells: the basic unit of structure and function
  • Tissues: groups of cells that perform a specific function
  • Organs: groups of tissues that work together to perform a specific function
  • Organ Systems: groups of organs that work together to maintain homeostasis

Nervous System

• Function: recognizes and coordinates the body's response to internal and external environments
• Structures:
  • Brain
  • Spinal cord
  • Peripheral nerves
• The nervous system is divided into:
  • Central Nervous System (CNS): brain and spinal cord
  • Peripheral Nervous System (PNS): nerves that connect the CNS to the rest of the body

Brain

• The brain is the control center of the body
• The cerebrum is the largest region of the brain, responsible for voluntary activities such as movement, sensation, and cognition
• The cerebellum coordinates muscle movements and maintains posture and balance
• The brain stem connects the brain to the spinal cord and regulates basic functions such as heart rate and breathing

Spinal Cord

• The spinal cord is a long, thin, tube-like structure that extends from the base of the brain down to the lower back
• It is the main communications link between the brain and the rest of the body
• The spinal cord is protected by the vertebrae and meninges

Peripheral Nervous System

• The PNS is divided into:
  • Sensory Division: transmits impulses from sense organs to the CNS
  • Motor Division: transmits impulses from the CNS to muscles and glands
• The autonomic nervous system is a subdivision of the PNS that regulates involuntary functions such as heart rate and digestion

Circulatory System

• Function: brings oxygen, nutrients, and hormones to cells; removes waste products
• Structures:
  • Heart
  • Blood vessels (arteries, capillaries, and veins)
  • Blood
• The heart pumps blood throughout the body, supplying oxygen and nutrients to cells and removing waste products

Heart

• The heart is a muscular organ that pumps blood throughout the body
• The heart has four chambers: right and left atria, and right and left ventricles
• The heartbeat is regulated by the sinoatrial node, a group of cardiac muscle cells in the right atrium

Blood Vessels

• Arteries: carry oxygen-rich blood away from the heart to the rest of the body
• Capillaries: allow for the exchange of oxygen and nutrients for waste products
• Veins: carry oxygen-poor blood back to the heart

Integumentary System

• Function: protects the body from external damage, regulates body temperature, and aids in the senses of touch and feel

• Structures:

  • Skin
  • Hair
  • Nails
  • Sweat and oil glands

• The skin is the largest organ of the body, and it has many different functions, including protecting the body from infection and injury.### Skin Structure and Function

• Cells in the inner layer of the epidermis undergo rapid cell division, producing new cells that push older cells to the surface of the skin.

• As older cells move upward, they become flattened and their organelles disintegrate, and they start producing keratin, a tough, fibrous protein.

• Melanocytes in the epidermis produce melanin, a dark pigment that helps protect the skin from damage by absorbing ultraviolet rays from the sun.

• Differences in skin color are caused by the amount of melanin produced and the distribution of melanocytes.

Dermis

• The dermis lies beneath the epidermis and contains collagen fibers, blood vessels, nerve endings, glands, sensory receptors, smooth muscles, and hair follicles.
• The skin interacts with other body systems to maintain homeostasis, regulating body temperature by constricting or widening blood vessels.
• The dermis contains two major types of glands: sweat glands, which produce perspiration to help regulate body temperature, and sebaceous glands, which produce sebum to keep the epidermis flexible and waterproof.

Human Body Systems

Skeletal System

• Functions: supports the body, protects internal organs, allows movement, stores mineral reserves, and provides a site for blood cell formation.
• Structures: bones, cartilage, ligaments, and tendons.

Muscular System

• Functions: works with the skeletal system to produce voluntary movement, helps to circulate blood, and moves through the digestive system.
• Structures: skeletal muscle, smooth muscle, and cardiac muscle.

Respiratory System

• Function: provides oxygen needed for cellular respiration and removes excess carbon dioxide from the body.
• Structures: nose, pharynx, larynx, trachea, bronchi, bronchioles, and lungs.

Digestive System

• Function: converts food into simpler molecules that can be used by the body and absorbs food, eliminating wastes.
• Structures: mouth, pharynx, esophagus, stomach, small and large intestine, and rectum.

Excretory System

• Function: eliminates waste products from the body, maintaining homeostasis.
• Structures: skin, lungs, kidneys, ureters, urinary bladder, and urethra.

Endocrine System

• Function: controls growth, development, and metabolism, maintaining homeostasis.
• Structures: hypothalamus, pituitary, thyroid, parathyroid, adrenals, pancreas, ovaries, and testes.

Reproductive System

• Function: produces reproductive cells; in females, nurtures and protects the developing embryo.
• Structures: testes, epididymis, vas deferens, urethra, and penis (in males); ovaries, fallopian tubes, uterus, and vagina (in females).

Lymphatic/Immune System

• Function: helps protect the body from diseases, collects fluid lost from blood vessels, and returns the fluid to the circulatory system.
• Structures: white blood cells, thymus, spleen, lymph nodes, and lymph vessels.