Human Body Organization

Levels of Organization

• The human body is organized in levels, from simplest to most complex.
• Cells are the basic unit of life.
• Tissues are clusters of cells performing a similar function.
• Organs are made of tissues that perform one specific function.
• Organ systems are groups of organs that perform a specific purpose in the human body.
• The 11 organ systems maintain homeostasis in the human body.

Cell Types

• Muscle tissue is the most abundant tissue, and controls internal and external movement.
• Epithelial tissue covers the body and organs, as well as lining organs and vessels.
• Connective tissue holds organs in place with ligaments and tendons.
• Nervous tissue receives and analyzes internal and external messages, directing responses.

11 Human Body Systems

• Nervous system.
• Integumentary system.
• Respiratory system.
• Digestive system.
• Excretory system.
• Skeletal system.
• Muscular system.
• Circulatory system.
• Endocrine system.
• Reproductive system.
• Lymphatic (immune) system.

Circulatory System

• The circulatory system delivers oxygenated blood for cellular respiration.
• The cell type is muscle.
• The heart pumps deoxygenated blood to the lungs for oxygenation, then to the rest of the body through the aorta.
• Valves regulate blood flow between the heart's chambers.

Circulatory System Interactions

• Lungs exchange oxygen and carbon dioxide with the circulatory system. The circulatory system picks up nutrients from the digestive system for transport.
• The excretory system filters blood to remove toxins, with the circulatory system.
• The nervous system regulates heartbeat and blood pressure.

Nervous System

• The nervous system coordinates the body's response to internal and external changes.
• The cell type for the nervous system is the nerve.
• The brain is the control center, where all processes are relayed.
• The brain consists of the cerebrum (controls thought and senses) and the cerebellum (controls motor functions).
• The spinal cord sends instructions from the brain to the rest of the body, and vice versa.
• Organisms with a major nerve cord are classified as chordates.
• Nerves conduct impulses to muscle cells throughout the body.

Nerves

• Nerves are neurons clustered into bundles of fibers (axons).
• Sensory nerves carry impulses from sense organs to the brain and spinal cord.
• Motor nerves relay messages from the brain or spinal cord to other organs.
• Interneurons connect sensory and motor neurons.
• A Synapse is a point where a neuron transfers an impulse to another cell.

Central Nervous System (CNS)

• The CNS is the control center of the human nervous system
• The brain contains 100 billion cells (neurons).
• The cerebrum is the largest part of the brain, responsible for learning, intelligence, and judgment.
• The cerebellum coordinates and balances muscle actions (posture, movement, balance).
• The brainstem regulates blood pressure, heart rate, breathing, and swallowing; including the thalamus, hypothalamus, midbrain, pons, and medulla oblongata.

Organ Systems Interactions (Nervous System)

• The nervous system interacts with all other body systems.

Respiratory System

• The respiratory system provides oxygen for cellular respiration and removes carbon dioxide.
• The cell type is epithelial.
• The nose is the internal entry and exit point for air.
• The pharynx serves as a passageway for both air and food.
• The larynx is the voicebox, where vocal chords vibrate to produce sound.
• The trachea, or windpipe, connects the pharynx to the lungs, with the epiglottis preventing food from entering.
• Bronchi are the two large passageways that lead from the trachea to the lungs.
• Bronchioles are subdivisions of the bronchi.
• Alveoli are tiny air sacs at the end of bronchioles where capillaries exchange gases with the blood.
• The lungs contain alveoli, bronchi, and connective tissue.
• The diaphragm is the muscle that causes breathing; hiccups are involuntary contractions of the diaphragm.
• Alveoli are air sacs with thin walls surrounded by blood capillaries.
• Oxygen gas is at a higher concentration in the alveoli than in the blood and diffuses into the blood through a layer of cells.
• Carbon dioxide is at a higher concentration in the blood than the alveoli and diffuses into the alveoli through a layer of cells.
• Alveoli are covered in a lipoprotein layer to prevent collapsing during exhalation.

Organ System Interactions (respiratory system)

• The respiratory system interacts directly with the circulatory system.
• The respiratory system interacts indirectly with the immune system, using the lining of the nasal and bronchiol cavities/tubes.
• The respiratory system interacts with the nervous system (smell and taste) for regulation of breathing.

Digestive System

• The digestive system converts food particles into simpler micromolecules for bloodstream absorption.
• Cell types are epithelial and muscle.
• The mouth chews and grinds up food.
• Saliva begins the chemical breakdown in the mouth.
• The esophagus connects the mouth to the stomach.
• The stomach secretes strong acid (pH = 2) to break down food.
• Food broken down in the stomach and mixed with digestive juices is called chyme.
• The pancreas secretes digestive enzymes and insulin to regulate blood sugar levels; it also helps neutralize stomach acid.
• The liver produces bile, which breaks down fats in foods.
• The gallbladder stores bile for future use.
• After digestion, the small intestine absorbs chyme into the bloodstream; villi on the intestine propel the chyme.
• The large intestine removes water from the chyme and prepares waste for excretion.

Organ system interactions of the digestive system

• The circulatory system moves nutrients to other parts of the body.
• The nervous system regulates peristaltic activity.
• The endocrine system uses hormones to regulate appetite and digestive enzyme release.
• The excretory system removes solid waste.

Lymphatic/Immune System

• The lymphatic/immune system removes infectious diseases and other pathogens.
• The cell type is epithelial.
• The skin, the integumentary system, is the body's first line of defense.
• White blood cells recognize disease agents (antigens) and create antibodies to tag and remove these antigens.
• Phagocytes are white blood cells that eat and destroy antigens.
• Lymph nodes help restore fluid lost by the blood and return it to the circulatory system.
• The spleen produces and stores white blood cells.
• The thymus is the site of white blood cell maturation.

Organ System Interactions (lymphatic/immune system)

• The integumentary system serves as the first line of defense.
• The respiratory system uses mucus membranes.
• The circulatory system transports antibodies and white blood cells.
• The endocrine system provides a chemical stimulus response.
• The Excretory and Digestive System work together for the elimination of pathogens.

Integumentary System

• The integumentary system functions in temperature regulation, waste removal, sensory information, and protection.
• The largest organ of the body is skin, which has two layers.
• Skin, hair, nails.
• The cell type is epithelial.

Hair Functions

• Hair may absorb radiation from the sun.
• Hair reduces loss of heat.
• Hair filters out dust and dirt.
• Hair shows gender.
• Hair is sensitive to movement.

Nail Function

• Nails protect tips of fingers and toes.
• Nails help pick up small objects.
• Nails enhance sensation of the finger by acting as a counterforce.
• Nails allow for scratching.

The Epidermis

• The epidermis is the outermost layer of skin.
• The epidermis is made of layers of epithelial cells.
• The outermost layer of cells is flattened, dead, and keratin filled.
• Keratin makes skin tough and waterproof.
• Skin replaces cells instead of repairing them.
• Epidermis generates cells at its base which move upwards.
• Epidermal cells contain melanin, a pigment that absorbs UV radiation.
• Melanin ranges from reddish brown to black.

Epidermis Layers

• Keratin is a tough, flexible protein.
• Melanocytes produce melanin.

Dermis Layers

• The dermis supports the epidermis.
• The dermis contains nerve endings, blood vessels, and smooth muscles.
• Sweat glands are controlled by the nervous system.
• Sebaceous glands produce oily secretions that help keep the epidermis flexible and waterproof.

Subcutaneous Tissue

• Located beneath the dermis.
• Connective tissue made of fat.
• It's a shock absorber, insulator, and energy storage
• Anchors skin to underlying organs.
• Thickness varies throughout the body.

Organ System Interactions (integumentary system)

• Immune system serves as the first line of defense.
• Circulatory system brings nutrients and water.
• Excretory system releases sweat.
• Nervous system has a sense of touch.
• Endocrine - thermoregulation.

Endocrine System

• The endocrine system controls growth, development, metabolism, and reproduction through hormones.
• Major organs include the hypothalamus, pituitary gland, thyroid, parathyroid, adrenal glands, pancreas, testes, and ovaries.
• The cell type is epithelial.

Describing the Endocrine System

• Controls all the metabolic activities of the body.
• A series of glands produce and release chemical messengers, generally into the bloodstream.
• Chemical messengers are called hormones and impact the behavior of cells.
• Only cells with receptors respond to hormones.

Glands of the Endocrine System

• The major gland is the pituitary gland, which produces many of the hormones that regulate the endocrine glands.
• The hypothalamus controls the pituitary gland.
• Other glands include the thyroid, parathyroid, adrenal, pancreas, ovaries, and testes.

Hormones Examples

• Thyroid secretes thyroxine, which regulates metabolic rate of cells.
• Adrenal medulla secretes adrenaline and noradrenaline, which prepare the body for "fight or flight".
• Pancreas secretes insulin, which regulates the amount of sugar in bloodstream.
• Posterior pituitary secretes oxytocin, which stimulates contractions of uterus during childbirth.

Endocrine System Interactions

• The endocrine system interacts with all others to regulate, especially with the nervous and circulatory systems.

Excretory System

• The excretory system rids the body of wastes, including excess water and salts.
• The cell type is epithelial.
• Kidneys filter waste-laden blood, filtering urea, excess water, and other waste products.
• Filtered waste travels through the ureter to the urinary bladder.
• The rectum passes out solid waste.

Organ System Interaction (excretory system)

• Circulatory system filters blood.
• Digestive system removes undigested food.
• Nervous system provides response & regulation.
• Endocrine system provides response regulation.

Ways to Excrete

• Skin - sweat glands remove excess water and salts from the body.
• Lungs - expel carbon dioxide.

Skeletal System

• The skeletal system provides structure and support to the human body.
• Bones generate new blood cells (in the marrow) and require calcium for strength.
• Major bones include the femur, humerus, radius and ulna, cranium, sternum, clavicle, fibula and tibia, vertebrae, scalpula, pelvic bone, coccyx, and phalanges.

Skeletal System Cells

• Osteocytes maintain bones.
• Bone marrow produce white and red blood cells.

Joints, Ligaments, Tendons and Cartilage

• Joints are where bones meet and can withstand pressure.
• Ligaments are strong bands of connective tissue that hold joints together and prevent them from moving too far.
• Tendons are strips of dense connective tissue attached to bone.
• Cartilage is light weight, strong, flexible tissue.

Other Systems Interactions (skeletal system)

• Nervous controls movement.
• Muscular system movement.
• Circulatory oxygen & nutrients.
• Digestive facilitates digestion (stomach & peristaltic activity).
• Excretory releases Sweat.

Reproductive System

• The reproductive system produces, matures, nourishes, and stores gametes.
• For the first six weeks of development, embryos are identical regardless of sex.
• Y chromosome presence in the seventh week causes testes development and androgen production to develop male physical characteristics and reproductive structures.
• The cell type is epithelial.

Interactions with other systems (reproductive)

• Endocrine provides hormones for gamete production & reproductive cycle.
• Nervous system.
• Circulatory system.

Muscular System

• The muscular system works with the skeletal and nervous system to produce body movement and blood circulation.
• Muscle cells are fibrous and muscle contractions can be voluntary or involuntary.
• Muscle makes up 40–50% of the body mass.
• Major muscles include biceps, triceps, glutes, and hamstrings, and deltoids.

Three Types of Muscles

• Skeletal muscles are attached to bones, voluntary control, multinucleated, striated.
• Smooth muscles comprise internal organs (except heart), one nucleus, nonstriated, involuntary control
• Cardiac muscles control the heart, one nucleus, striated, involuntary control

Muscular Structure

• Tendons are dense strips of connective tissue.
• Flexors are muscles that cause a joint to bend.
• Extensors are muscles that cause the joint to straighten.
• Actin & myosin enable muscles to contract.
• Myofibrils are fibers found in muscle cells that enable them to contract
• Sarcomeres are a basic unit of contraction in skeletal and cardiac muscles.
• The Origin is where the muscle pulls against.
• The Insertion is the bone where muscle moves.

How Muscles Work

• Muscles work in antagonistic pairs (opposite each other) and are always in a state of slight contraction.
• Muscles always pull, bones do not push them.
• Flexors decrease the angle of the joint (bends), examples are biceps and hamstrings.
• Extensors opens a joint to normal position (extends), examples triceps and quadriceps.
• Abductors move bone away from midline of the body, like the deltoids.
• Adductors move bone towards the midline of the body, like the latisimus dorsi.

Interactions (muscular systems)

• Circulatory pumps the heart. Skeletal enables movement.
• The nervous system enables movement & vision (focus).
• The digestive aids the stomach & peristaltic activity.
• The endocrine - release of some hormones a& enzymes