The Human Body Plan

Body Cavities
There are two major body cavities: the dorsal cavity and the ventral cavity
Dorsal cavity contains the organs of the nervous system, which can be further divided into:
Cranial cavity surrounds and protects the brain and is lined with protective tissue called dura mater. The spinal cord enters the bottom of the cranium through the foramen magnum, which continues as the brain stem.
Spinal cavity surrounds and protects the spinal cord
Ventral cavity divided into two regions by a wall of muscle called the diaphragm. These two regions are :
The upper region, also called the thoracic cavity, contains the heart, lungs, trachea, and esophagus, which is protected by the ribs, breastbone, and spine. It extends from the bottom of the neck to the diaphragm.
The lower region, also called the abdominal cavity, contains the digestive, reproductive, and excretory system organs.
Body Tissues
Tissues are a group of cells similar in structure and function. There are four main types in the human body. Tissue Types
Cells in each tissue are shaped and arranged to perform a particular function.
Muscle Tissue- Composed of cells that contract
Skeletal muscle tissue moves bones
Cardiac muscle tissue pumps blood throughout the body (heart)
Smooth muscle tissue moves substances throughout the body (organs)
Nervous Tissue- Consists of cells that transmit messages throughout the body
Nerve cells respond to changes in all parts of the body.
The brain, spinal cord, sensory organs, and nerves are composed of this.
Epithelial tissue - Protects, secretes, and absorbs
These tissues bind tightly together, forming a solid sheet that covers, protects, or lines a body part.
Skin and cells that line organs of the body cavity are examples.
Connective tissues - Support the body.
Types of connective tissues: bone, cartilage, tendons, fat, blood, and lymph, which are embedded in or surrounded by a substance called a matrix.
A matrix can be: solid, semisolid, or liquid in some cases.
Cartilage cells, tendons, and fat cells have a fibrous matrix, while bone cells have a crystalline matrix, and blood has a liquid matrix.
Organs and Organ Systems
An organ is made up of several types of tissues that together perform a bodily function.
An example of an organ is the heart or the stomach.
An organ system is made up of groups of organs that work together.
An example of an organ system is the digestive system or the circulatory system.

The Skeletal System

Skeleton--the human body contains 206 bones that are organized into an internal framework. At birth, the human body contains around 350 tiny bones.
The internal framework of the body is called the endoskeleton.
Diagram -- Skeletal System
Diagram -- Locomotion- limb movement
Diagram -- Locomotion- skeleton
Skeletal Function
The functions of the bones are to support the muscle and organs, give shape and structure to the body, and protect delicate internal organs.
Bones also store calcium and phosphorous and minerals used in certain vital metabolic processes. The internal portion of the bone manufactures blood cells. 
Skeleton and Bone Structure
The skeleton is composed of two parts:
The axial skeleton, which consists of 80 bones such as the ribs, spine, sternum, sacrum, and cranium.
The appendicular skeleton is made up of 126 bones
arms, legs, pelvis, and shoulders are part of the appendicular skeleton
Bones are also made up of organic and inorganic materials
Internal Structure of the long bone Diagram -- Bone- structure
Periosteum is the tough outer membrane of the bone
The membrane contains a network of blood vessels that supplies living bone cells with oxygen and nutrients and carries away carbon dioxide.
Compact bone is a hard material under the periosteum
It is composed of rings of mineral crystals and protein fibers.
Osteocytes are the living bone cells found throughout the mineral rings.
Haversian canal is a channel in the center of each ring
It contains nerves and blood vessels, and enables the bones to endure stress they receive upon impact with solid objects.
Spongy Bone is the interior to the compact bone
It is a network of connective tissues, and fills the interior of the knob-like end of long bones such as the arms and legs. It adds strength without adding much weight. Bones must not weigh very much in order to allow movement.
Bone Marrow is the soft tissue in the centers and ends of long bones where blood cells are produced.
The red marrow consists of blood vessels, fibers, and cells manufacturing erythrocytes and white blood cells.
It is found in spongy bone, and the end of long bones.
Yellow marrow consists mostly of fat cells which serve as energy.
It is found in the shafts of long bones.
Bone Development
Ossification is the process by which bones develop. There are two types:
Bones develop as cartilage and then form as bones. Diagram -- Bone and cartilage- structure
Cartilage is a tough, flexible, connective tissue.
Bones develop directly from embryonic connective tissue.
During fetal development, in the second month the skeleton is composed of cartilage. By the third month osteocytes develop in the cartilage which then forms into bone, although some areas remain cartilage.
Epiphyseal Plate is a band of cartilage located near the distal end of a long bone.
When a person has stopped growing, bone replaces the cartilage in the epiphyseal plate allowing no more longitudinal growth; the person has reached full height.
A joint is the place at which two bones meet Diagram -- Joints- types
Ligaments are connective tissue in a joint
There are three kinds of joints:
Fixed joints- do not move. Diagram -- Locomotion- joints
The bones in the skull where connective tissues are in the structure to absorb impact and prevent broken bones.
Semi-movable joints- semi-movable
The spinal column which allows the body to bend and twist.
Movable joints- movable
The elbow, or the wrist which allows movement forwards and backwards.
Bursa is a fluid filled sac that adds additional cushioning between the bones, and prevents the ends of bones from wearing away.
Three types of injuries to the joints are:
Bursitis is when the bursa becomes inflamed due to the overuse of a joint.
Sprain is when ligaments rounding the joints are torn.
Rheumatoid arthritis is a condition in which the synovia membrane becomes inflamed and grows thicker. The fibrous tissues become ossified, immobilizing the joints, and fusing joints together.

The Muscular System

The Muscular System - The bones can't move by themselves. Only the attachment of muscle to the bones allows movement.
Diagram- 1--Muscular System
Diagram- 2--Muscular System
Diagram- 3--Muscular System
Muscle Types
A muscle is a contractile organ consisting of many cells. There are 3 types of muscle tissues: Diagram -- Muscles- types
Skeletal muscle is attached to the bone.
It has striations, which are dark bands located at right angles to the long axis of the muscles. It is a voluntary muscle, which means that it is under the conscious control of the brain.
Diagram -- Muscles- types [skeletal striated muscles]
Cardiac muscle makes up the walls of the heart.
It is striated. It contracts because of electrical signals received from a special nerve center. This is what causes the heart to beat. It is involuntary, which means that the brain has no conscious control over its movement.
Diagram -- Muscles- types [cardiac muscles]
Smooth muscle is found in the walls of the stomach, intestines, and blood vessels. It has no striations, and it is involuntary.
The Muscle Cell
Skeletal muscle cells, called muscle fiber, are multinucleate and contains 1000 to 2000 threadlike myofibrils.
Sarcomere is the functional unit of muscular contraction.
Two protein filaments are present in sarcomere. They are myosin and actin.
` How Muscles Contract
A nerve impulse reaches a muscle. A stimulus reaching the motor end plate ( junction of a nerve branch and a muscle) causes a specialized membrane of the muscle to release calcium into the muscle cytoplasm.
Causes shape changes in protein molecules allowing the binding of myosin heads to actin filaments. The myosin head bends inward, pulling the actin filament toward the center of the sarcomere.
The myosin is then released and it uses the energy from ATP to return the myosin heads to their original position. This action is repeated, moving the muscle fibers and therefore, the muscles.
How Muscles move Bone
Muscles are connected to bones in two places:
The origin which is the part of the bone that remains stationary when the muscle contracts.
The insertion is the part that moves when the muscle contracts.
Skeletal muscles function in opposing pairs.

The Integumentary System

Integumentary System - Skin, hair, and nails protect our insides from the outside. Diagram -- Skin Structure
Skin is waterproof, it regulates body temperature, retains body fluids, protects against disease, and eliminates waste products.
The epidermis is the outer layer of skin. The outer cells are dead, and all the cells are filled with keratin, a protein that gives the skin its rough, leathery texture, and makes it waterproof.
The dermis is the inner layer of skin. The cells that make it up are alive, and it contains nerves, blood, and lymph vessels. The nerves allow the reception of environmental signals. The blood vessels help regulate body temperature, and the lymph helps protect against infection. A layer of fat below the dermis stores food for energy.
A hair root is produced at the base of the hair follicle, which is a deep pocket that extends into the dermis. The hair shaft (the part of the hair outside the skin) is made of keratin and needs no nourishment, because it is no longer alive. Oil from glands in the skin keeps the hair shaft from drying out and breaking off.
Nails form from root cells in the epidermis. As new cells form, the nail grows longer. Nails are also made up of keratin.
Glands release secretions through ducts. The main glands are the sweat glands and the oil glands.
Sweat glands release excess salts, water, and urea to regulate body temperature. If the body is too hot, the sweat glands release sweat, which evaporates and cools the body.
The oil glands release sebum, which helps keep the skin soft and waterproof.

A pigment, determines if the skin will be light or dark, and it protects the skin from harmful ultraviolet light by absorbing it.

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Wadsworth - Tissues, Organ Sysem and Homeostasis
Body Quest
The Virtual Body
The Mississippi School for Mathemataics and Science - Skeletal  Systems
Scenic Heights Elementary School and The University of West Florida Curriculum Project - Skeletal System
Aspen Middle School - Skeletal System
Click The Bones and They Will Speak
University of Leeds(U.K.) Bones
University of Leeds(U.K.) Joints
How the Body Works --   Bone
The Mississippi School for Mathemataics and Science - Muscular System
Scenic Heights Elementary School and The University of West Florida Curriculum Project - Muscular System
Aspen Middle School - Muscular System
The Muscle Page for Kids!
Wadswoth- Skeletal and Muscular Systems
University of Leeds (U.K) Muscles
Human Body Atlas - Muscles and Bones of the Body
Montana State University - Integumentary System



Mayo Health O@sis Skin Conditions
Health Clinic USA -- Skin Diseases
Mayo Health O@sis Bones, Muscles & Joints
Health Clinic USA -- Bone Diseases
Health Clinic USA -- Musculoskeletal Diseases
Mayo Health O@sis Arthritis and Rheumatology
Health Clinic USA -- Arthritis
Arthritis and arthritis-related disorders
Osteoporosis and osteoporosis-related disorders
ALS and ALS-related disorders
TENNIS ELBOW (Lateral Epicondylitis)