Video Details

Animations and Images 2011 Collection

Grade Levels:	3 - 12
Core Subject(s):	Science
Website:	http://www.uen.org/emedia
Usage rights:	Download and retain personal copies in perpetuity.

Availability information for this program

Episodes:

• A Journey Through Geologic Time: Theory of Continental Drift

  The theory of continental drift states that the present-day continents were joined together in a supercontinent called Pangaea. Over time, the continents drifted away from each other to their present-day positions.

  Length:	00:00:22

• Activities of Plants: Fertilization in Plants

  Fertilization is the combining of male and female sex cells. When a pollen grain touches the top of the pistil, called the stigma, it forms a tube through which male sex cells travel downward into the ovary. An egg is fertilized inside the ovary.

  Length:	00:00:23

• Activities of Plants: Photosynthesis I

  In the process of photosynthesis, plants take in carbon dioxide and water and using light from the sun, they produce sugar and oxygen.

  Length:	00:00:08

• Amazing Amphibians and Reptiles: Amniotic egg

  The amniotic egg is watertight, and consists of several layers of membranes. Among other structures it contains a food source for the developing embryo in the form of a yolk.

  Length:	00:00:12

• Amazing Amphibians and Reptiles: Amphibian circulation

  Amphibians possess a three-chambered heart that pumps blood throughout the body via a network of blood vessels.

  Length:	00:00:19

• Balanced Diet: Food Pyramid

  The food pyramid depicts the five major food groups: grains, fruit, vegetables, milk, meat and beans.

  Length:	00:00:18

• Blood and Circulation: Oxygen in Body

  Oxygen mixes with blood in the lungs and is then pumped throughout the body.

  Length:	00:00:05

• Bones and Muscles: Ball and Socket Joint

  A ball and socket joint is made of a bone with a rounded end that fits inside a cup-like pocket of another bone, enabling bones to move in a circle. Hip joints and shoulder joints are examples.

  Length:	00:00:14

• Circulation and Respiration: Capillaries I

  Capillaries are the smallest blood vessels.

  Length:	00:00:04

• Circulation and Respiration: Pumping Heart

  The heart is responsible for circulating blood throughout your body.

  Length:	00:00:05

• Classifying Life: Embryology

  Embryology is the study of the development of embryos. By comparing embryological development of different organisms, scientists can identify relationships.

  Length:	00:00:14

• Digestion and Excretion: Enzymes

  Enzymes play an important role in chemical digestion.

  Length:	00:00:07

• Digestion and Excretion: Esophagus

  The esophagus is a muscular tube that carries food from the mouth to the stomach through waves of muscular contractions called peristalsis.

  Length:	00:00:13

• Digestion and excretion: Kidneys

  The main organs of the human urinary system include two bean-shaped kidneys located at the bottom of the rib cage near the back. Kidneys perform the very important job of removing nitrogen-containing wastes from the blood.

  Length:	00:00:10

• Exploring Plant Reproduction: Angiosperm Life Cycle

  When a pollen grain lands on the sticky stigma, it forms a pollen tube through the thin style to the ovary. Once in the ovary, the pollen tube enters the ovule. Two haploid sperm nuclei then enter the embryo sac.

  Length:	00:01:12

• Exploring Plant Reproduction: Bryophyte Life Cycle

  In most bryophytes, the haploid gametophyte phase is dominant. It's what we commonly recognize. Bryophytes tend to produce separate male and female gametophytes.

  Length:	00:00:55

• Exploring Plant Reproduction: Fern Life Cycle

  When a mature spore is released and lands in a suitable location, it develops into a tiny, heart-shaped haploid gametophyte form called a "prothallus."

  Length:	00:00:40

• Exploring Plant Reproduction: Gymnosperm Life Cycle

  Pollen is transferred via the wind or by other means from the male pollen cone to the female seed cone. Of the millions of pollen grains released from sporangia, some land on the scales of female cones near an opening called the "micropyle."

  Length:	00:00:41

• Exploring Plant Reproduction: Megaspore

  Female cones, seen here, possess ovules that produce egg cells.

  Length:	00:00:07

• Exploring Plant Reproduction: Ovaries in Flower

  Gametophytes are quite small in angiosperms and develop in the flower of the sporophyte plant. Female eggs form in ovules inside the ovary of the flower.

  Length:	00:00:21

• Exploring Plant Reproduction: Pollen Grains in Flowers

  In the male reproductive part of the flower, haploid spores called "microspores" are produced in a structure called the "anther." The microspores consist of two-celled male gametophytes that together make up a pollen grain.

  Length:	00:00:15

• Exploring the Digestive and Excretory Systems: Nephron

  The fundamental filtering units in the kidneys are nephrons. Each kidney contains over one million nephrons. Most of the fluid is returned or reabsorbed by the bloodstream along with other substances needed by the body.

  Length:	00:00:19

• Exploring the Digestive and Excretory Systems: Small intestine III

  The small intestine is a hollow tube that is only about 2.5 centimeters in diameter, but it stretches about 7 meters in length. The chemical digestion of carbohydrates and proteins is completed in the small intestine.

  Length:	00:00:23

• Exploring the Digestive and Excretory Systems: Urinary system I

  One of the most important ways the body excretes wastes is via specialized structures in the urinary system.

  Length:	00:00:08

• Exploring the Digestive and Excretory Systems: Urine

  Urine passes out the kidneys to the bladder through small tubes called ureters. From time to time urine is emptied from the bladder through the urethra.

  Length:	00:00:12

• Food and Digestion: Esophagus peristalsis

  Food travels through the esophagus via rhythmic muscular contractions referred to as peristalsis.

  Length:	00:00:09

• Food and Digestion: Villi absorbing nutrients

  Nutrients are absorbed into tiny blood vessels found inside villi. Blood then carries nutrients throughout the body.

  Length:	00:00:08

• Genetics in Our Lives: Fertilized egg

  A male sex cell unites with a female sex cell to form a fertilized egg.

  Length:	00:00:24

• Healthy Circulatory and Respiratory Systems: Capillaries II

  Capillaries are microscopic vessels where food and gases are exchanged with cells of the body.

  Length:	00:00:08

• Healthy Circulatory and Respiratory Systems: Damaged Heart

  When the coronary arteries, which supply blood to the heart, become clogged with fat, it is more difficult for blood to nourish heart muscles. When blood flow to the heart is cut off or greatly reduced, a heart attack might occur, damaging the heart.

  Length:	00:00:15

• Healthy Circulatory and Respiratory Systems: Fatty Deposits in Arteries

  Atherosclerosis is a condition in which fatty substances are deposited on the inner walls of arteries. It is often the cause of heart attacks.

  Length:	00:00:08

• Healthy Circulatory and Respiratory Systems: Oxygen Rich Blood

  Oxygen-rich blood is circulated throughout the body.

  Length:	00:00:04

• Healthy Digestive and Excretory Systems: Heartburn

  Heartburn is caused by the back flow of acidic stomach contents into the esophagus. It is also called acid reflux.

  Length:	00:00:16

• Healthy Digestive and Excretory Systems: Kidney

  The two kidneys in the body monitor levels of salt and water concentrations. Waste material, including excess water, is filtered out of the blood by kidneys in the form of urine.

  Length:	00:00:25

• Healthy Digestive and Excretory Systems: Peristalsis II

  Food travels down the esophagus into the stomach through a series of involuntary muscular contractions called peristalsis.

  Length:	00:00:08

• Healthy Digestive and Excretory Systems: Sweat Glands

  Salt, water, and excess materials are excreted from the body by sweat glands, which are located in the skin and excrete waste through tiny openings in the skin called pores.

  Length:	00:00:15

• Healthy Nervous and Endocrine Systems: Central Nervous System

  The central nervous system includes the brain, which is protected by the skull, and the spinal cord, which is protected by vertebrae, making up the backbone.

  Length:	00:00:15

• Healthy Nervous and Endocrine Systems: Concussion

  A concussion is an injury to the brain that can be caused by a hard hit to the head or violent shaking of the brain.

  Length:	00:00:08

• Healthy Nervous and Endocrine Systems: Endocrine System II

  The endocrine system in the body's regulator. It is composed of tissues and organs throughout the body that secrete hormones.

  Length:	00:00:07

• Healthy Nervous and Endocrine Systems: Nerve Cell

  A nerve cell, also called a neuron, is the primary cellular building block in the nervous system.

  Length:	00:00:19

• Healthy Nervous and Endocrine Systems: Nervous System

  There are two main sections of the nervous system - the central nervous system and the peripheral nervous system - which work together.

  Length:	00:00:10

• Healthy Nervous and Endocrine Systems: Peripheral Nervous System I

  The peripheral nervous system contains nerves that form a network throughout the body that directs voluntary and involuntary activities. The spinal cord connects the brain to nerves throughout the body.

  Length:	00:00:10

• Healthy Nervous and Endocrine Systems: Peripheral Nervous System II

  The peripheral nervous system consists of all the body's nerves located outside of the spinal cord and brain.

  Length:	00:00:04

• Healthy Nervous and Endocrine Systems: Skull II

  The skull protects the brain.

  Length:	00:00:04

• Healthy Skeletal and Muscular Systems: Breast Bone and Ribs

  The breast bone and ribs protect the lungs and heart.

  Length:	00:00:05

• Healthy Skeletal and Muscular Systems: Cartilage II

  Cartilage is found at the end of bones and joints. It enables the ends of bones to move smoothly against each other.

  Length:	00:00:13

• Healthy Skeletal and Muscular Systems: Hinge Joint

  A joint is the place where two bones come together. The knee is an example of a hinge joint.

  Length:	00:00:05

• Healthy Skeletal and Muscular Systems: Red Blood Cells II

  Some bones produce red blood cells.

  Length:	00:00:08

• Healthy Skeletal and Muscular Systems: Skeletal Muscle

  This moving arm depicts skeletal muscle, or voluntary muscles, which move when we want them to move. Skeletal muscles usually work in pairs, meaning that when one contracts the other relaxes.

  Length:	00:00:08

• Healthy Skeletal and Muscular Systems: Sprain

  Sprains occur when ligaments at a joint are stressed or torn.

  Length:	00:00:09

• Healthy Skeletal and Muscular Systems: Tendonitis

  Tendonitis is an inflammation of the tendon.

  Length:	00:00:13

• Healthy Skeletal and Muscular Systems: Tendons

  Tendons are tissues that attach muscles to bones.

  Length:	00:00:03

• Investigating Circulation: Artery

  Arteries are blood vessels with thick, elastic, muscular walls that carry oxygen-rich blood from the heart to the body.

  Length:	00:00:08

• Investigating Circulation: Artherosclerosis

  A common cause of high blood pressure is a disease called "atherosclerosis." Atherosclerosis is a condition characterized by narrowing of the arteries. This is due to an accumulation of fatty deposits called "plaque" on the inner walls of arteries.

  Length:	00:00:20

• Investigating Circulation: Blood Type

  Red blood cells have two possible carbohydrates which coat their surface. The letters "A" and "B" refer to these two different types of carbohydrates.

  Length:	00:00:11

• Investigating Circulation: Blood Zoom

  As you know from getting cut, blood is a fluid. Almost 55% of the total volume of blood is made up of a liquid called "plasma." Plasma consists mainly of water.

  Length:	00:00:07

• Investigating Circulation: Capillaries

  Thin-walled blood vessels called capillaries are so small that blood vessels flow through them in single file. Gases, nutrients, and wastes are exchanged through the thin walls of capillaries.

  Length:	00:00:19

• Investigating Circulation: Capillaries III

  Thin-walled blood vessels called "capillaries" are so small that blood cells flow through them in single file. Gases, nutrients, and wastes are exchanged through the thin walls of capillaries. Capillaries form branches that connect to arteries and veins.

  Length:	00:00:11

• Investigating Circulation: Heart Beat

  The pumping action of the heart has two main periods: a period of relaxation called the "diastole," and a period of contraction called "systole."

  Length:	00:00:04

• Investigating Circulation: Heart Cutaway

  From the left ventricle, oxygen-rich blood enters the largest artery in the body, the aorta. Arteries stemming off the aorta carry oxygen-rich blood to all parts of the body.

  Length:	00:00:19

• Investigating Circulation: Heart Turn

  The heart is made up of four main chambers or hollow compartments. The septum, a thick wall of tissue, separates the hearts' right side and left side. Right and left is referred to as if the heart were in your own body.

  Length:	00:00:09

• Investigating Circulation: Human Circulatory System

  Your body also has a vast network of pipelike structures called "blood vessels" that transport blood.

  Length:	00:00:10

• Investigating Circulation: Platelets

  Platelets consist of cell fragments that play a key role in blood clotting. Through a series of reactions, platelets help weave a net across a cut or injury. Without clotting, you'd bleed to death.

  Length:	00:00:10

• Investigating Circulation: Pulse

  If you place your fingers on the underside of your wrist, you can feel blood pulsing in an artery. Veins, another type of blood vessel, return oxygen-depleted blood to the heart.

  Length:	00:00:13

• Investigating Circulation: Red and White Blood Cells

  The two main types of blood cells include red blood cells and white blood cells.

  Length:	00:00:06

• Investigating Circulation: Type A Blood

  A person that has blood type A has the type of A carbohydrate in their blood cells,

  Length:	00:00:06

• Investigating Circulation: Type AB Blood

  A person with type AB blood has both carbohydrates, and a person with type O blood has neither of these carbohydrates

  Length:	00:00:06

• Investigating Circulation: Type B Blood

  A person that has blood type B has the B-type carbohydrate in their blood cells

  Length:	00:00:06

• Investigating Circulation: Type O Blood

  A person with type O blood has neither type A or B carbohydrates

  Length:	00:00:05

• Investigating Circulation: Veins

  Veins, another type of blood vessel, return oxygen-depleted blood to the heart.

  Length:	00:00:05

• Investigating Plant Structure and Function: Leaf Internal

  The interior layers of a leaf: palisade layer, spongy mesophyll, which allows oxygen, carbon dioxide, and water vapor to exchange between cells and the atmosphere; and stomata, through which gases enter and exit the leaf.

  Length:	00:00:40

• Investigating the Immune System: 1914 Flu Antibody

  Antibodies do not destroy antigens. Instead, they mark them for T cell destruction by binding to them.

  Length:	00:00:03

• Investigating the Immune System: Antibody

  Antibodies do not destroy antigens. Instead, they mark them for T cell destruction by binding to them.

  Length:	00:00:07

• Investigating the Immune System: Antigen

  An antigen is a substance on the surface of a cell that identifies the cell as a pathogen

  Length:	00:00:07

• Investigating the Immune System: B Cell

  The main function of B cells is to recognize specific antigens and produce specific antibodies.

  Length:	00:00:08

• Investigating the Immune System: Interferon

  Pathogens can cause infected cells to produce a protein called "interferon." This substance causes nearby uninfected cells to produce enzymes that block the reproduction of pathogens.

  Length:	00:00:14

• Investigating the Immune System: Killer T Cells

  Cytotoxic T cells, also called "killer T cells," attack dangerous cells by producing a protein that bursts the cell membrane.

  Length:	00:00:08

• Investigating the Immune System: Lymph Nodes

  Lymph is transported through lymph vessels. Special structures called "lymph nodes" filter lymph and store white blood cells. When the body is fighting an infection, white blood cells are produced in great numbers.

  Length:	00:00:09

• Investigating the Immune System: Organs of the Immune System

  Important structures in the lymphatic system include the tonsils, thymus gland, and the spleen. The spleen is very important because it removes worn-out red blood cells, platelets, bacteria, and other things from the blood.

  Length:	00:00:10

• Investigating the Immune System: Phagocyte I

  Phagocytes are leukocytes that engulf unwanted cells and pathogens in a nonspecific manner.

  Length:	00:00:05

• Investigating the Immune System: Phagocyte II

  Macrophages are the largest leukocytes, and lymphocytes are leukocytes involved in specific defense activities.

  Length:	00:00:08

• Investigating the Immune System: T Cells

  T cells are lymphocytes that seek and destroy pathogens. There are several types of T cells.

  Length:	00:00:06

• Investigating the Immune System: White Blood Cells Grow

  When the body is fighting an infection, white blood cells are produced in great numbers.

  Length:	00:00:05

• Light: Behavior of Light

  Light energy travels as an electromagnetic wave, and as a stream of moving particles called photons.

  Length:	00:00:13

• Light: Dispersion

  When light passes through a prism, the glass slows the light down. Different colors in white light have different wavelengths. Each wavelength is refracted a different amount, causing them to separate into different colors in the process of dispersion.

  Length:	00:00:22

• Magnificent Mammals: Placenta

  The placenta is a structure that enables the exchange of vital nutrients, oxygen, carbon dioxide, and wastes between the mother and the embryo.

  Length:	00:00:11

• Moving Muscles and Bones: Skeleton Clip

  A skeleton is the body's framework.

  Length:	00:00:09

• Nutrition Basics: Carbohydrates

  The chemical structure of the first carbohydrate is simpler than the second carbohydrate, which is a complex carbohydrate. Complex carbohydrates are broken down slowly by the body and release sugars into the blood stream over a longer period of time.

  Length:	00:00:10

• Nutrition Basics: Chyme

  The stomach releases acids and juices, which further break down food into a thick, pasty material called chyme.

  Length:	00:00:09

• Photosynthesis and Plant Responses: Vascular Tissue

  Plants possess vascular tissue, which is a system of tiny tubes that move food and water throughout the plant.

  Length:	00:00:07

• Photosynthesis: C4 Pathway

  An extra photosynthetic pathway, called the "C4 pathway," acts as a carbon dioxide pump that provides more fixed carbon to the Calvin cycle. This allows C4 plants to fix CO2 more rapidly, thus producing more glucose.

  Length:	00:00:24

• Photosynthesis: Calvin Cycle

  Carbon fixation takes place via a series of complex reactions collectively referred to as the "Calvin cycle." The starting and ending point in the Calvin cycle is a 5-carbon sugar called "ribulose bisphosphate," or RuBP for short.

  Length:	00:01:16

• Photosynthesis: CAM Pathway

  To prevent water loss, they close their stomates during the day. This inhibits the entry of carbon dioxide. To compensate, they take in CO2 during the night when stomates are open.

  Length:	00:00:26

• Photosynthesis: Photosynthesis

  Light-dependent reactions occur in areas of the thylakoid referred to as "photosystems." There are two different types of photosystems called "photosystem I" and "photosystem II."

  Length:	00:01:43

• Plant Growth, Development, and Response: Germination II

  Once a seed has made its home in the soil, its next step is to begin germination. But germination does not always occur right away. Seeds may remain dormant in the soil anywhere from a few weeks to many years.

  Length:	00:00:18

• Plant Growth, Development, and Response: Seed Structure

  Above the point of attachment of the cotyledons is a structure called the "epicotyl." Later, it gives rise to the upper part of the stem, the leaves, and the terminal bud.

  Length:	00:00:34

• Plant Reproduction: Sexual Reproduction of Ferns

  In the sexual reproduction of ferns, spores are released into the air and eventually fall to the ground to form a prothallus in the gametophyte phase. The gametophyte produces eggs and sperm. The sperm swims to the egg and fertilization occurs.

  Length:	00:00:32

• Plant Structure and Function: Plant Vascular

  Underneath the bark of a tree is a layer of phloem, which consists of tubular cells that move food from the leaves and stem throughout the body of the plant. Cambium, another type of vascular tissue, is responsible for making new xylem and phloem.

  Length:	00:00:29

• Reproduction and Development: Implantation

  The blastocyst becomes embedded in the wall of the uterus in a process called "implantation." This signifies the beginning of pregnancy. Following implantation, the blastocyst further develops into a three-layered structure, the gastrula.

  Length:	00:00:21

• Reproduction and Development: Menstrual Cycle Graph

  Let's begin at day one, when the pituitary glands release two hormones-- follicle-stimulating hormone, or FSH for short, and luteinizing hormone, or LH. FSH stimulates a follicle to develop into an egg.

  Length:	00:01:49

• Reproduction and Development: Oviducts

  The egg then travels through the oviduct, also called the "fallopian tube." If fertilization occurs, it happens here. Then, the egg travels to the thick-walled, muscular uterus.

  Length:	00:00:12

• Reproduction and Development: Ovulation

  When the egg sac matures, its follicle moves to the surface of the ovary, breaks open, and releases the egg.

  Length:	00:00:09

• Reproduction and Development: Prostate

  The two vas deferens empty to the urethra, the same structure through which urine empties. As sperm enter the urethra, the seminal vesicles, Cowper's glands, and the prostate gland secrete fluids into the urethra that nourishes and protects sperm.

  Length:	00:00:17

• Reproduction and Development: Testes

  Sperm cells are produced in the seminiferous tubules but then move to the epididymis where they mature and are stored. Mature sperm exit the epididymis through a tube called the "vas deferens."

  Length:	00:00:05

• Reproduction and Development: Uterus and Ovaries

  It's in the uterus that the fetus develops. At the bottom of the uterus is the cervix. That's the opening into the vagina, which leads to the outside of the body.

  Length:	00:00:03

• Reproduction and Development: Zygote

  The zygote then slowly moves through the fallopian tube as it gradually undergoes a series of cell divisions referred to as "cleavage." In the process of cleavage, the zygote repeatedly divides and develops into a ball of cells called a "morula."

  Length:	00:00:06

• Respiration: Alveoli

  Small bronchioles end in tiny air sacs call "alveoli," arranged kind of like grapes on a stem. Alveoli consist of thin membranes lined with a dense network of capillaries across which gas exchange occurs with blood cells.

  Length:	00:00:21

• Respiration: Bronchi and Alveoli

  In the lungs, bronchi branch out into smaller and smaller tubes called "bronchioles."

  Length:	00:00:28

• Respiration: Diaphragm

  The diaphragm is a sheet of muscle below the lungs separating the chest cavity from the abdomen. When the diaphragm and the intercostal muscles contract, the size of the chest cavity increases.

  Length:	00:00:45

• Respiration: Lungs

  Under the ribs in your chest are two very important structures called "lungs." Lungs are the site of gas exchange.

  Length:	00:00:09

• Respiration: Pneumonia

  The body responds to these agents by accumulating fluid and debris in the alveoli. This inhibits the ability of the lungs to exchange oxygen. Another relatively common respiratory problem is bronchitis.

  Length:	00:00:11

• Respiration: Respiratory Center

  Breathing is controlled in a part of the brain generally referred to as the "respiratory center." Feedback is continually given to this part of the brain to adjust the rate of breathing.

  Length:	00:00:12

• Respiration: Respiratory Organs

  The nasal cavity and upper part of the respiratory system is lined with mucus membranes and small hairs that help accomplish these tasks. From the nasal cavity or mouth, air enters the pharynx, or throat.

  Length:	00:01:22

• Respiration: Smoking and Alveoli

  Smoking makes it difficult for oxygen to be exchanged through alveoli. It's estimated that at least one-third of the smoke inhaled from smoking coats alveoli with particles.

  Length:	00:00:09

• Senses: Chemoreceptors

  Chemoreceptors for smell, specifically referred to as "olfactory cells," are concentrated in mucus membranes lining the upper nasal cavity.

  Length:	00:00:11

• Senses: Cochlea I

  Inside the inner ear is a coiled, fluid-filled structure called the "cochlea." It plays a key role in hearing.

  Length:	00:00:06

• Senses: Cochlea II

  inside the cochlea are specialized hair cells that are sensitive to vibrations of sound waves. The hair cells transmit nerve impulses to the cochlear nerve that, in turn, transmits impulses to the brain, specifically, the cerebral cortex.

  Length:	00:00:09

• Senses: Ear

  The middle ear region, located further inside the head, contains a delicate structure called the "tympanic membrane," commonly referred to as the "eardrum." The eardrum vibrates when sound waves make contact with it.

  Length:	00:00:39

• Senses: Eustachian Tube

  A small canal called the "Eustachian tube" leads from the middle ear to the throat. It helps equalize air pressure between the middle ear and the external environment.

  Length:	00:00:12

• Senses: Middle Ear

  The eardrum vibrates when sound waves make contact with it. In turn, vibrations are transmitted to several tiny bones-- the hammer, anvil, and stirrup.

  Length:	00:00:09

• Senses: Semicircular Canals

  Structures in the inner ear, called "semicircular canals," contain fluid which help the body maintain balance. When the head changes position, receptors in the canals detect a change in the direction of the fluid.

  Length:	00:00:08

• Senses: Sound Wave II

  The sounds we hear actually consist of disturbances in the air called "sound waves."

  Length:	00:00:05

• Senses: Spinal Cord II

  The spinal cord consists of a long bundle of neurons running the length of the back.

  Length:	00:00:07

• Skin, Skeletal, and Muscular Systems: Compact bone

  Compact bone is very dense and provides support. It is found in the shafts of long bones such as in the legs and arms.

  Length:	00:00:11

• Skin, Skeletal, and Muscular Systems: Major Bones

  You're probably familiar with some of the major bones, such as the femur, tibia, ulna, radius, humerus, and ribs.

  Length:	00:00:26

• Skin, Skeletal, and Muscular Systems: Marrow

  Red marrow found in long bones, breastbone, cranium, and vertebrae is responsible for producing red blood cells, platelets, and some types of white blood cells. Yellow marrow consists of fat cells, and is found in the hollow centers of long bones.

  Length:	00:00:30

• Skin, Skeletal, and Muscular Systems: Moving muscles

  Because a muscle exerts force only when it contracts, it moves a bone in just one direction. Therefore muscles often work in pairs, with muscles moving in opposite directions.

  Length:	00:00:27

• Skin, Skeletal, and Muscular Systems: Muscle fibers

  Skeletal muscle is made up of muscle fibers.

  Length:	00:00:06

• Skin, Skeletal, and Muscular Systems: Myofibrils

  Muscle fibers are made of myofibrils which are small cylinder-shaped structures. Myofibrils are made up of tiny filaments. Some of these filaments are thin and others are thick.

  Length:	00:00:28

• Skin, Skeletal, and Muscular Systems: Osteocytes

  Osteoblasts make new bone cells called osteocytes. In some types of bones osteocytes are arranged in circular patterns around a common cavity called the Haversian canal.

  Length:	00:00:23

• Skin, Skeletal, and Muscular Systems: Periosteum

  Bones are covered by a tough membrane called periosteum. Its primary goal is to make new bone for growth and repairs. Small blood vessels branch through the periosteum to move nutrient-rich blood to reach deeper into the bone.

  Length:	00:00:17

• Skin, Skeletal, and Muscular Systems: Skin

  The outer layer of skin, the epidermis, consists of tightly packed epithelial cells that form a layer only about as thick as a piece of paper. The dermis lies below the epidermis and consists of thick layer of connective tissue.

  Length:	00:01:14

• The Amazing Nervous System: Neuron Action Potential

  Nerve impulses occur when the electrical charge across a neuron cell membrane reverses. Nerve impulse is also referred to as "action potential" and involves the reversal and restoring of charges across a neuron cell membrane.

  Length:	00:00:27

• The Amazing Nervous System: Neurons

  Neurons are one kind of nerve cell that transmit signals throughout the body.

  Length:	00:00:05

• The Amazing Nervous System: Parts of the Brain

  The brain has three main parts-- the brain stem, the cerebellum, and the cerebrum. Let's start with the brain stem. It consists of the midbrain, pons, and medulla oblongata. Located just above the brainstem are the thalamus and hypothalamus.

  Length:	00:00:22

• The Amazing Nervous System: Reflex Arc

  When you respond involuntarily to a hot object, a reflex arc begins when sensory neurons in your hand detect pain. Sensory neurons then carry information in the form of a nerve impulse to the spinal cord.

  Length:	00:00:31

• The Amazing Nervous System: Spinal Cord III

  The backbone encases the spinal cord, a bundle of nerves that play a key role in the central nervous system.

  Length:	00:00:11

• The Amazing Nervous System: Synapse

  Nerve impulses move across spaces called "synapses" via specific chemical messengers referred to as "neurotransmitters." Special structures located on the ends of axons release neurotransmitters into the synapse when an impulse is received.

  Length:	00:00:34

• The Cell: Cell Division

  The splitting of a parent cell into two new cells is called cell division.

  Length:	00:00:11

• The Cell: Chloroplasts

  Chloroplasts are the places in plant cells where photosynthesis occurs. Chloroplasts contain chlorophyll.

  Length:	00:00:11

• The Cell: Materials Cross Cell Membrane

  Food and water move through the cell membrane into the animal cell, while waste products cross the cell membrane to exit the cell.

  Length:	00:00:10

• The Classification of Organisms: Classification

  There are eight main taxonomic levels in the modern taxonomic hierarchy.

  Length:	00:00:43

• The Classification of Organisms: Classification of fly

  Going from the broad to the specific, the house fly is in the domain Eukarya, the kingdom Animalia, the phylum Arthropoda, the class Insecta, the order Diptera, the family Muscidae, genus Musca, and species domestica.

  Length:	00:00:30

• The Life of Birds: Bird digestion

  When birds eat, food passes from the mouth to an enlarged part of the esophagus called the crop. Here food is stored and softened, then passes to the gizzard, then travels to the intestine where nutrients are absorbed.

  Length:	00:00:39

• The Outer Planets: Meteorite Hitting Earth

  Many scientists believe a meteorite struck Earth over 65 million years ago and is responsible for altering Earth's weather, which led to the extinction of dinosaurs and other life.

  Length:	00:00:13

• Volcanoes and Earthquakes: Cinder Cone Volcano

  Cinder cone volcanoes are the result of smaller fountain-like eruptions that cause a cone to form.

  Length:	00:00:08

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