Human Body Systems

Human Body

• Systems

Organization of the Human Body

• Cells: Basic unit of structure and function.

• Human Body Tissues:

  • Connective

  • Epithelial

  • Nervous

  • Cardiac

• Human Organs:

  • Lungs

  • Liver

  • Thyroid

  • Brain

  • Intestines

  • Bladder

  • Heart

  • Stomach

  • Kidneys

• Human Organ Systems:

  • Respiratory system

  • Reproductive system

  • Integumentary system

  • Urinary system

  • Skeletal system

  • Digestive system

  • Nervous system

  • Lymphatic system

  • Endocrine system

  • Circulatory system

  • Muscular system

Human Body Tissues

• Connective tissue

• Nervous tissue

• Muscle tissue:

  • Skeletal muscle

  • Cardiac muscle

  • Smooth muscle

• Epithelial tissue

Homeostasis and Feedback

• Homeostasis: The body works to maintain a controlled and stable internal environment.

• Feedback Loops: There are two types of feedback loops to control homeostasis:

  • Positive feedback loop

  • Negative feedback loop

• Negative Feedback Loop Example (Blood Glucose):

  • Stimulus: Blood glucose level rises.

  • Pancreas:

    • Stimulates glucose uptake by cells.

    • Stimulates glycogen formation in the liver.

  • Liver/Tissue cells: Glucose is converted to glycogen.

  • Balance: Normal blood glucose level (about 90 mg/100 ml).

  • Imbalance: Blood glucose falls to normal range or rises to normal range.

  • Glucagon: Stimulates glycogen breakdown in the liver to increase blood glucose levels.

• Positive Feedback Loop Example (Childbirth):

  • Stimulus: Contractions

  • Oxytocin induces contractions.

  • Contractions cause release of prostaglandins.

  • Brain stimulates pituitary to secrete more oxytocin.

• All body systems work together to control feedback loops.

Basic Anatomical Positions and Directional Terms

• In order to learn about the body, you should know basic anatomical terms.

• Anatomical Position: Body is standing erect with feet parallel and the arms hanging at the sides with the palms facing forward.

• Directional Terms:

  • Anterior/Posterior:

    • Anterior: Situated near or toward the front of the body.

    • Posterior: Situated near or toward the back of the body.

  • Superior/Inferior:

    • Superior: Situated toward the upper part or head of the body, positioned above another organ or structure. Cranial refers to the head end.

    • Inferior: Situated toward the lower part of the body or positioned below another organ or structure. Caudal refers to the tail end.

  • Medial/Lateral:

    • Medial: Closer to the midline of the body or a structure, being internal as opposed to external.

    • Lateral: Farther away, in the direction of either side, from the midline of the body or a structure.

  • Proximal/Distal:

    • Proximal: Toward or nearest the trunk or the point of origin of a part.

    • Distal: Away from or farthest from the trunk or the point of origin of a part.

  • Superficial/Deep:

    • Superficial: Near the outer surface of the body (e.g., skin is superficial to the muscle).

    • Deep: Further away from the surface of the body (e.g., muscular layer is deep to the skin but superficial to the intestines).

Planes of Reference

• Body Planes: These are based on four imaginary planes that pass through the body in the anatomical position.

  1. Sagittal

  2. Mid-sagittal (median) plane

  3. Frontal (coronal) plane

  4. Transverse plane (cross section)

• Directional terms.

• Directional terms tell us where body parts are located with reference to the body in anatomical position.

  • anterior (ventral)

  • posterior (dorsal)

  • superior

  • medial

  • proximal

  • superficial

  • inferior

  • lateral

  • distal

  • deep

The Digestive System

• Function: To digest (break down) food into smaller molecules so they can diffuse into cells.

• Organs: Mouth, esophagus, stomach, liver, small intestine, large intestine, rectum, anus, accessory organs.

• Mouth:

  • Teeth: break up food (mechanical digestion).

  • Saliva: chemical digestion.

    • Amylase enzyme: digests starch into simple sugars.

    • Anti-bacterial enzymes: kill bacteria that enter mouth with food.

• Swallowing (& not choking):

  • Epiglottis: flap of cartilage.

    • Closes trachea (windpipe) when swallowing.

    • Food travels down esophagus.

• Esophagus:

  • Peristalsis: involuntary muscle contractions to move food along.

• Stomach:

  • HCl (pH 2): disinfects food by killing bacteria.

  • Pepsin, an enzyme, digests protein.

  • Fun fact: The stomach can stretch to fit approximately 2 liters of food.

• Small Intestine:

  • Chemical digestion.

    • Digest carbohydrates - Amylase from pancreas.

    • Digest proteins - Trypsin & chymotrypsin from pancreas.

    • Digest lipids (fats) - Bile from liver & lipase from pancreas.

  • Diffusion of nutrients into cells.

  • Parts:

    • Duodenum

    • Jejunum

    • Ileum

• Absorption in Small Intestines

  • Absorption through villi.

    • finger-like projections

    • Increases surface area for absorption.

• Pancreas:

  • Produces digestive enzymes.

    • Trypsin & chymotrypsin: digest proteins.

    • Amylase: digest starch.

    • Lipase: digest lipids.

  • Buffers: Neutralizes acid from stomach

• Liver:

  • Produces bile: breaks up fats.

  • Gallbladder stores bile, but does not make it (that is why you can have your gall bladder removed).

• Large Intestines (colon):

  • Reabsorbs water.

    • Uses approximately 9 liters of water every day in digestive juices.

    • 90% of water is reabsorbed.

    • If not enough water is reabsorbed: diarrhea (which can be fatal).

    • Too much water reabsorbed: leads to constipation.

    • Reabsorbed by diffusion.

• Appendix:

  • Vestigial organ.

• Rectum and Anus:

  • Last section of large intestines.

  • Eliminate feces.

  • What's left over?

    • Undigested materials: Mainly cellulose from plants (fiber) which keeps everything moving and cleans out intestines.

    • Masses of bacteria.

• Ulcers:

  • Caused by bacterial infection of stomach

    • H.pylori bacteria

    • Cure with antibiotics

The Excretory System

• Function: Removes metabolic waste from the body.

  • Metabolic waste: $CO_2$, urine, water, salts.

• Major Organs:

  • Lungs: $CO<em>2$ and $H</em>2O$

  • Skin: Salts and $H_2O$

  • Kidneys: $H_2O$ and urea --> urine.

• Human Kidney:

  • Maintains homeostasis.

  • Filters waste products from the blood.

  • Regulates water content of the blood.

• What is Urea?

  • When digesting proteins, excess amino acids are released into the bloodstream.

  • The liver converts these potentially poisonous amino acids into urea.

• Urine Composition:

  • 95% Water

  • 2% Urea

  • 0.05% Ammonia

  • 0.18% Sulphate

  • 0.12% Phosphate

  • 0.6% Chloride

  • 0.01% Magnesium

  • 0.015% Calcium

  • 0.6% Potassium

  • 0.1% Sodium

  • 0.1% Creatinine

  • 0.03% Uric acid

• Kidney Stones:

  • Occur when calcium magnesium or uric acid salts in the urine crystalize.

  • Stones block the ureter and cause pain.

  • Stones are treated with an ultrasound to break apart the stones.

• Dialysis: Homeostasis by Machine

  • Blood is removed from the body through a tube inserted in the arm and is pumped through a special tube that acts like the kidneys.

The Cardiovascular System (including blood and lymphatic systems)

• Just like the plumbing system in your home carries water through a series of pipes to different parts of a house, the circulatory system carries blood through a series of blood vessels to different parts of the body

• Blood is a type of connective tissue containing both dissolved substances and specialized cells.

• Functions: Transports nutrients and oxygen to cells and wastes away from them.

• Major Organ: Heart.

• What's in Blood?:

  • Blood cells.

  • Nutrients.

  • Oxygen.

  • Carbon Dioxide.

  • Hormones.

  • Antibodies.

  • Waste Products.

• Blood collects oxygen from the lungs, nutrients from the digestive tract, and waste products from tissues.

• Blood helps regulate internal environment factors, such as body temperature. Also, components in blood help fight infections, and can even form clots to repair damaged blood vessels.

• The human body contains 4 to 6 liters of blood, which is about 8% of the total body mass.

• About 45% of the volume of blood consists of cells, which are suspended in the other 55%: a straw colored fluid called plasma.

  • Plasma is about 90% water and 10% dissolved gases, salts, nutrients, enzymes, hormones, waste products and proteins.

• The Human Heart

  • Function: Pump blood throughout the body

• Transport of Materials Throughout the Body:

  • Blood from the heart

    • Artery: Carries blood away from the heart.

  • Blood to the heart

    • Vein: Carries blood back into the heart.

  • Capillary: Carries blood to and from the body's cells.

    • Inside the Capillaries: Diffusion of materials (gases, nutrients, and waste).

• Red Blood Cells: Carry Oxygen

  • Red blood cells transport oxygen, white blood cells perform a variety of protective functions, and platelets help in the clotting process.

  • Platelets are actually fragments of cells derived from larger cells in red bone marrow.

  • The most numerous cells in the blood are the red blood cells. They transport oxygen, and get their color from hemoglobin.

  • Hemoglobin is the iron containing protein that binds to oxygen in the lungs and transports it to tissues throughout the body.

• White blood cells are the "army" of the circulatory system. They guard against infection, fight parasites and attack bacteria.

• Red blood cells are shaped like disks that are thinner in the center than along the edges. They are produced from cells in red bone marrow, and circulate for an average of 120 days before they are worn out from squeezing through narrow capillaries.

• The cellular portion of blood consists of red blood cells, white blood cells, and platelets.

• Blood clotting is made possible by plasma proteins and cell fragments called platelets that are formed from certain large cells in red bone marrow breaking into many pieces. When platelets come into contact with the edges of a broken blood vessel, their surfaces become very sticky, and a cluster of platelets develop around the wound.

• Other white blood cells, known as lymphocytes, are involved in the immune response.

Respiratory System

• Function: Gas exchange

  • Inhales oxygen for cellular respiration to make ATP

  • Exhales carbon dioxide as a waste product.

• Major Organ: Lungs

• Other Organs: Trachea, Bronchi, Bronchioles, Alveoli

• Lungs:

  • Spongy texture with high surface area to allow more diffusion of oxygen.

  • Alveoli: Millions of tiny air sacs.

  • Moist lining: Mucus traps dust and pollen.

  • Covered by cilia: Hair-like extensions of cells that move mucous upward to clear out lungs

• Breathing:

  • Diaphragm moves down and expands chest cavity pulling air into lungs.

• Gas Exchange in the Lungs:

  • Occurs in the alveoli of the lungs.

  • Oxygen diffuses from the lung to the blood, and carbon dioxide diffuses from the blood to the lungs.

• Breathing and Homeostasis:

  • Need to regulate oxygen in and carbon dioxide out in order to ensure adequate energy (ATP) production.

Nervous System

• Introduction

  • Regulates all body processes.

  • Maintains homeostasis.

  • Coordination and Control.

• Human Nervous System

  • Central nervous system (CNS) includes the brain and spinal cord. The Peripheral nervous system includes all the nerves outside of the CNS.

• The Brain

  • Cerebrum

    • Voluntary activity.

    • Interprets sensory impulses.

    • Responsible for memory, thinking and reasoning.

  • Cerebellum

    • Coordination and balance.

    • Homeostasis.

  • Medulla (Brain stem)

    • Controls Involuntary activities including breathing, heart beat, blood flow, digestion.

• Spinal Cord

  • Hollow tube composed of nerve fibers that carry impulses to and from the brain.

  • Controls reflexes.

• Neurons

  • Nerve cells where electrical and chemical impulses travel

    • Most specialized cell in animals

    • Longest cells

      • Blue whale neuron: 10 - 30 meters

      • Giraffe Axon: 5 meters

      • Human neuron: 1 - 2 meters

  • Nervous systems allows for 1 millisecond response time

  • The brain is made up of billions of nerve cells, also known as neurons.

  • It is estimated that the adult human brain controls $10^{11}$ neurons.

• Parts of a Neuron

  1. Cell body: Controls all activities of the neuron

  2. Dendrites: Fibers that receive messages from other neurons

  3. Axon: Carries messages from the cell body to the axon terminals

  4. Terminal branches: Relays messages to the next neuron.

• Myelin Sheath

  • Axon coated with insulation made of myelin cells

    • speeds signal

      • Signal hops from node to node

      • 330 mph vs. 11 mph

• Synapse

  • Space between nerve cells

    • 1st neuron releases a chemical called a neurotransmitter to communicate with the next neuron

    • Where drugs affect the nervous system

• Reflexes

  • Automatic response to a stimulus that does not require conscious thought - rapid response

    • Message travels to the spinal cord and back to the muscles. It does NOT go to the brain!

• Types of Neurons

  • Sensory neuron: (from senses)

  • Interneuron: (brain & spinal cord)

  • Motor neuron: (to muscle)

• The Reflex Arc

  1. Stimulus - Change in the environment

  2. Receptor - Detect the stimulus

  3. Sensory Neuron - Carries the impulse to the spinal cord

  4. Interneuron - Located in the spinal cord in-between the sensory and motor neurons

  5. Motor neuron-carries the message away from the spinal cord

  6. Effector - muscle or gland

The Muscular System

• Movement is the function of the muscular system.

• More than 40% of the mass of the average human body is muscle

• Muscle tissue is found everywhere in the body, not just beneath the skin. There are 3 types of muscle tissue:

  • skeletal

  • smooth

  • cardiac

• Each type of muscle is specialized for specific function in the body

  1. Skeletal Muscle

     • Skeletal muscles are usually attached to bones (hence their name).

     • They are responsible for voluntary movements, like typing on a keyboard, dancing, or winking.

  2. Smooth Muscle

     • Smooth muscles are usually not under voluntary control.

     • They are spindle shaped, have only one nucleus, and are not striated.

  3. Cardiac Muscle

     • Cardiac muscle is found in only one place: the heart.

     • Cardiac muscle is striated like skeletal muscle, but its cells are smaller. It is similar to smooth muscle because it is also not under voluntary control.

• Muscle Contraction

  • Most skeletal muscles work in opposing pairs. When one muscle contracts, the other relaxes. The muscle fibers in skeletal muscles are made up of smaller structures called myofibrils.

    • Each myofibril is made up of even smaller structures called filaments.

      • The thick filaments contain a protein called myosin.

      • The thin filaments are made up mainly of a protein called actin.

The Skeletal System

• To retain their shape, all organisms need some type of structural support.

• The human skeleton is composed of a type of connective tissue called bone.

• Bones and other connective tissues, such as cartilage and ligaments, form the skeletal system.

• The skeleton supports the body, protects internal organs, provides for movement, stores mineral reserves, and provides a site for blood cell formation.

• Bones are a solid network of living cells and protein fibers that are surrounded by deposits of calcium salts.

• Bones are surrounded by a tough layer of connective tissue called the periosteum

• A place where one bone attaches to another bone is called a joint.

• Depending on its type of movement, a joint is classified as immovable (like where your the bones in the skull meet), slightly movable (like the bones between our vertebrae), or freely movable.

• There are 2 types of marrow:
  1.) yellow
  2.) red
  *Yellow marrow is made up mostly of fat cells, and red marrow produces red blood cells, some kinds of white blood cells, and cell fragments called platelets.

The Integumentary System

• The integumentary system (made up of skin, hair and nails), serves as the body's first defense against infection and injury, helps to regulate body temperature, removes waste products from the body, and provides protection against ultraviolet (UV) radiation from the sun.

  • Skin is the largest organ in the human body and has an acidic pH value (anywhere between 4.5-7) to help prevent bacteria and foreign material from growing on it.

  • The skin is made up of two main layers: the epidermis and the dermis.

  • Beneath the dermis is a layer of fat (the hypodermis) and loose connective tissue that helps insulate the body.

    • The epidermis has two layers: an outside layer of dead cells and an inner layer of living cells which constantly go through constant rapid cell division, and push older cells to the surface of the skin and creates a tough, flexible, waterproof covering on the surface of the skin.

  • The epidermis also contains melanocytes, which produce melanin: a dark brown pigment that helps protect the skin from damage by absorbing UV rays from the sun.

  • The dermis lies beneath the epidermis, and contains blood vessels, nerve endings, sensory receptors, smooth muscle, sweat glands, and hair fibers.

The Endocrine System

• Composed of glands that secrete HORMONES into the bloodstream.

• The Endocrine and Nervous systems act together to REGULATE the human body and maintain homeostasis.

• Hormones are specifically shaped chemical protein messengers that are released by endocrine glands.

• Responding to hormones: There is a lock and key system where hormones fit SPECIFIC receptors on to TARGET cells

• Endocrine Glands:

  1. Pineal: Melatonin

  2. Pituitary: many hormones: master gland

  3. Thyroid: Thyroxin

  4. Adrenal: Adrenaline

  5. Pancreas: Insulin, glucagon

  6. Ovary: Estrogen

  7. Testes: Testosterone

  8. Hypothalamus: Dopamine, Growth

• Pancreas: Secretes insulin and glucagon.

  • Insulin: lowers blood glucose levels

  • Glucagon: increases blood glucose levels

Reproductive System

• The Male Reproductive System

  • Testis: Male Gonads

    • Produce male hormone: Testosterone

      • Controls secondary sex characteristics and the production of sperm

    • Produces sperm by meiosis

• The Female Reproductive System

  • Ovaries - Female Gonads

    • Produces eggs by meiosis

    • Produce female hormones estrogen and progesterone

The Immune System & Disease

• With pathogens (disease causing agents) all around us, it may seem like a miracle that you're not sick all the time. For that you can thank your immune system, a series of defenses that guard against disease.

• The immune system recognizes, attacks, destroys, and "remembers" each type of pathogen that enters the body. It does this by producing specialized cells that inactivate pathogens.

• The function of the immune system is to fight infection through the production of cells that inactivate foreign substances or cells. This process is called immunity.

• The immune system includes 2 general categories of defense mechanisms against infection:

  1. Nonspecific

  2. Specific

• Antigen: A substance that triggers this response is known as an antigen. Viruses, bacteria, and other pathogens may serve as antigens.