Science Study Guide for the TEAS

Human Anatomy and Physiology: The Urinary, Immune, and Skeletal Systems

Anatomy and Physiology of the Urinary System

The urinary system, or renal system, removes waste from the body and regulates the blood. Some references combine the urinary and reproductive systems into one and call it the genitourinary system. The urinary system is part of the larger excretory system, which includes the lungs, skin, and rectum as well.

Structure

This system is composed of the kidneys, ureters, bladder, and urethra.

Function

The kidneys filter the blood, converting waste into urine. The ureters are smooth, muscular tubes that transport urine from the kidneys to the bladder. Urine is stored in the bladder before being passed through the urethra and expelled.

Relationship to the Cardiovascular System

As well as removing wastes from the body, the urinary system has an important role to play in maintaining blood volume and blood pressure. As they filter the blood, the kidneys regulate the amount of water that is eliminated in the urine. The kidneys monitor changes in blood pressure, oxygen levels, and ion concentrations and secrete hormones to restore any imbalances in these areas.

Anatomy and Physiology of the Immune System

The immune system protects the body against disease. The immune system consists of several tissues and cells working together to monitor the body for both general and specific threats to homeostasis. It is vital to have a strong understanding of the immune system in order to work in the medical field.

Structure

The immune system consists of first-line defenses, such as the skin and mucus membranes, that block or trap pathogens before they can enter the body. The lymphatic system, composed of lymph nodes and lymphatic vessels, is tightly intertwined with the immune system. The bone marrow creates white blood cells that find and destroy pathogens.

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Function

White blood cells, or leukocytes, are produced and stored by the body. There are two general types of leukocytes: phagocytes, which destroy foreign cells, and lymphocytes, which are used to remember and recognize foreign organisms, enabling more efficient destruction. This system is divided into the innate and adaptive immune systems.

The Innate Immune System

The innate immune system is able to respond quickly to general threats. Humans are born with these responses. The innate immune system includes the skin and mucous membranes, as well as cells that destroy any foreign pathogen encountered.

The Adaptive Immune System

The adaptive immune system builds up over time as the body learns how to identify specific pathogens that attack the body. During an infection, the body creates antibodies that bind to target pathogens and signal the leukocytes to destroy them. When the pathogen is encountered again, the defenses are already in place to control it quickly. Vaccinations take advantage of the adaptive immune system by introducing weakened forms of a pathogen to build up the body’s defenses in advance of any possible infection.

Passive and Active Immunity

Active immunity refers to the body’s own defenses that build up over time to protect from infection. Passive immunity occurs in cases where antibodies are passed from one person to another, giving them temporary immunity. Natural examples of passive immunity are the immune cells that pass from mother to baby during fetal development and breastfeeding.

Relationship to Other Body Systems

The immune system works with the integumentary system, the lymphatic system, the circulatory system, and the skeletal system. The immune system can be thought of as having three lines of defense. First-line defenses occur before a pathogen can enter the bloodstream and include the skin, saliva, mucous membranes, hair, and stomach acid. Second-line defenses are innate immune cells in the bloodstream, and third-line defenses are the adaptive immune cells that target specific pathogens.

Anatomy and Physiology of the Skeletal System

The skeletal system supports the body, enables movement (in conjunction with the muscular system), protects internal organs, and generates blood cells. The skeletal system is divided into the axial skeleton (skull, vertebral column, and rib cage) and the appendicular skeleton (pelvis, shoulders, and limbs). Bones are made of protein fibers surrounded by calcium deposits.

Structure

The skeletal system consists of the bones of the body, as well as the supporting tissues that connect them. The bones vary in size, shape, and purpose. Some act as levers to move the body around, and some offer strength and protection.

Types of Bones

There are five types of bones in the human body:

• Long bones are cylindrical; some examples are the leg, arm, and finger bones.

• Flat bones are the thin bones that protect organs and join other bones together, such as the skull and shoulder blades.

• Short bones are about the same width and length and offer limited mobility. The wrist and ankle bones are short bones.

• Sesamoid bones are small and round, and they are located in tendons to help strengthen joints that are often compressed, like the patella in the knee joint.

• Irregular bones have a unique shape, like the vertebrae, for example.

Supportive Tissue

Supportive tissues include cartilage, tendons, and ligaments. Cartilage is a tough but flexible protein fiber that is a precursor to bone in a developing embryo and protects bones and joints by reducing friction. Ligaments are fibers that connect bones to each other at the joints. Tendons are made of strong connective tissue that anchors muscles to bones to allow movement to occur.

Joints

Joints form where bones come together. Joints that do not move, such as the ones connecting the bones in the skull, are suture joints. Hinge joints, like the elbows, bend and straighten in one direction. Pivot joints, like the neck bones, allow back-and-forth rotation. Ball and socket joints, found at the shoulders and hips, allow a range of motion in many directions. Ellipsoidal joints, like in the wrists, allow back-and-forth and up-and-down motion.

Bone Composition

The outer layer of bone is called compact bone, and it has networks of arteries and veins running through it. The inner layer is called spongy bone because of its appearance, but it is not soft like a sponge. The holes and spaces in the spongy bone allow the bone to be strong without being as heavy as solid bone would be. It also allows room for the bone marrow, which produces red and white blood cells and platelets.

Function

Bones serve multiple purposes. They provide a framework for the body itself, protect organs, produce red and white blood cells in the marrow, and store calcium, iron, and fat. Your most sensitive organs are protected by bones. The brain is protected by the skull and the heart and lungs are protected by the rib cage. The red and white blood cells produced in the marrow are essential for carrying oxygen and for full operation of the immune system.

Relationship to the Muscular System

In conjunction with muscles, bones allow for movement. Together they are referred to as the musculoskeletal system. The muscle attachments create levers out of long bones, such as your arm bones. When the muscle contracts, it pulls the bone up during flexion or straightens it out during extension. The muscles that attach to your skeleton are known as skeletal muscles.