Ch. 3: Human Organization
and Introduction to Homeostasis
(text pp. 61-78)
Human Biology (BIOL100)
In chapter 3 we will explore the basic organization of the cells of the human body
and organ systems
3) cell organelles.
7) organ systems.
is a mass of cells each of which performs a similar function. The four types of
tissue are epithelial, connective, muscular,
is a structure composed of two or more tissues which combine to perform a specific
function(s). Examples of organs are the stomach, heart, lungs, skin, etc.
An organ system
is composed of two or more organs which combine to perform a specific function(s).
Examples of organs systems are the cardiovascular system, muscular system, skeletal
system, nervous system, etc.
We will take a brief look at the body cavities
that contain and surround the various organs and organ systems of the human body.
Finally we will study homeostasis,
the attempts of the tissues, organs, and organ systems of the human body to maintain
a relatively constant internal environment regardless of the conditions in the external
I. Types of Tissues
There are four types of tissues: epithelial, connective, muscular,
Epithelial tissue consists of cells that cover the internal and external surfaces
of the body.
It functions to protect and allow for the secretion and absorbtion of substances out
of and into the body.
The shapes of the cells that make-up epithelial tissue are:
These cells can be arranged as a single layer called simple
or into multiple layers called stratified
Epithelial cells may hold cilia
and can form glands
that secrete their product into ducts or directly into the blood.
Connective tissue consists of cells dispersed in a non-cellular matrix
of several types.
It functions to bind other tissue types and the organs together, provides support
and protection, produces blood cells, and stores fat.
The types of connective tissue are:
1. Loose fibrous
2. Dense fibrous
- proteins matrix forms tendons and ligaments.
- store fat.
- rigid, mineralized matrix.
- plasma matrix containing erythrocytes, leukocytes, and thrombocytes.
Muscular tissue consists of cells called muscle fibers
Muscle fibers contain filaments of the proteins actin and myosin which allow the cell
to contract to produce movement.
The types of muscular tissue are:
or voluntary muscle
- multi-nucleate, striated cells. Contraction of skeletal muscle fibers is under
voluntary control. It is attached to bones via tendons.
or involuntary muscle
- single nucleus, cells are not striated. Contraction of smooth muscle fibers is
involuntary. It is located in many internal organs and blood vessels.
3. Cardiac muscle
- single nucleus, striated, branched cells. Contraction of cardiac muscle fibers
is involuntary. It is located in the heart.
Nervous tissue consists of cells called neurons
located in the brain, spinal cord, and nerves.
It functions to produce and conduct nervous impulses. These nervous impulses may
(internal and external stimuli), integrative
(within the brain and spinal cord), and motor
(to muscles and glands).
II. Body Cavities and Membranes
The internal organs are located within specific body cavities:
1) Dorsal cavity
a) Cranial cavity
- contains the brain.
b) Vertebral canal
- contains the spinal cord.
2) Ventral cavity
a) Thoracic cavity
- contains the heart (within pericardium) and lungs (within the pleura). Separated
from the abdominopelvic cavity by the diaphragm.
b) Abdominopelvic cavity
- contains the organs of the digestive, urinary, and reproductive system.
These cavities are lined by epithelial membranes:
1) Mucous membranes.
2) Serous membranes.
3) Synovial membranes.
III. Organ Systems
The organ systems of the human body work together to maintain homeostasis
1) Maintainance of the body
- the digestive, cardiovascular, lymphatic, respiratory, and urinary systems perform
processing and tranporting functions that maintain the normal conditions of the body.
2) Integumentary system
- the skin is sometimes called the integumentary system because it contains accessory
organs such as hair, nails, sweat, and oil glands.
3) Support and Movement
- the skeletal and muscular systems give the body support and allow it to move.
4) Integration and Control of the Body
- the nervous system receives sensory input from internal and external sensory receptors
and directs the musculoskeletal system and glands to respond to outside stimuli.
The endocrine system produces hormones.
5) Continuance of the Species
- The male and female reproductive systems contain the organs that produce gametes
(sex cells = sperm and eggs) and the ducts that make gametes available so that fertilization
Homeostasis is the dynamic equilibrium of the internal environment of the human body.
The internal environment consists of tissue fluid
, which bathes the cells and is derived from blood
All organ systems contribute to maintaining the relatively constant composition and
condition of the blood and tissue fluids in order that the cells may function normally.
Coordination of the activity organ systems in order to maintain homeostasis is achieved
through nervous and endocrine control.
A negative feedback mechanism
is utilized in both systems.