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HUMAN
BODY
I. The Human Body
A. Introduction
Humans are the most complex organisms on Earth, and every
cell in the human body must work together to keep functioning.
There are many levels of organization:
• 1. Cell - basic unit of structure and function in ALL
living things and usually are specialized for
a particular function.
• 2. Tissues- group of cells that perform a single
function.
4 types of tissue
a. Epithelial
• covers body surfaces, lines cavities, organs,
vessels. May contain glands for secretions or
cells with cilia. Examples include thyroid gland,
epicardium of heart, arteries & veins.
Epidermis
small intestine
kidney
b. Connective
• the most abundant and widespread tissue in the
body. Used for support, transport, storage,
and as connectors. Has a network of nonliving material called a matrix. Ex. Bone, blood,
cartilage.
c. Muscle
• able to generate electrical signals that create
force and movement. Ex. Skeletal muscle,
cardiac muscle, & smooth muscle.
d. Nerve
• specialized to generate and transmit electrical
signals to transfer information. Examples include
tissues of the brain and spinal cord.
PNS – ganglion
Blue stained Myelin sheath with red nuceli
3. Organ - group of tissues
working together for a
particular function.
4. Organ system - Group of
organs working together
to perform a function.
B. Organ Systems
• All the parts of the body work together to maintain the internal
conditions inside of a human.
1. Nervous system - Receives, processes, and responds to sensory
information: coordinates all body functions
2. Endocrine System - regulates homeostasis with chemicals called
hormones.
3. Skeletal System - protects and supports body parts.
4. Muscular System - produces movement.
5. Integumentary System- physical barrier against injury, dehydration,
pathogens.
6. Circulatory system - transports O2 and CO2, nutrients, and wastes.
7. Respiratory system - responsible for the exchange of O2 and Co2
8. Lymphatic System - destroys pathogens, fights infection.
9. Digestive System - breaks down food into absorbable monomers.
10. Urinary System - washes or cleans the blood; regulates blood volume.
11. Reproductive System – produces gametes; development of embryo in female
• Organ systems work together in the body to maintain homeostasis.
• Homeostasis - the process by which organisms keep internal and physical
conditions constant, or in internal harmony. This harmony is accomplished
by negative feedback mechanisms.
• Negative feedback - the process in which a stimulus produces a response
that opposes the original stimulus. (ex. House hold heater or AC(pg. 896) &
thyroid hormones)
• This process is fulfilled by the endocrine and nervous systems working
together.
• Endocrine system - may take hours to couple of days to affect the body.
• Nervous system - quick and rapid transmission to the body