Chapter 1

Chapter 1Chapter 1Introduction to Introduction to Human BodyHuman Body

Topical Outcome Topical Outcome • By the end of this topic you are able

to:-Differentiate the term of anatomy and

physiology– Identify and explain the levels of

organization and body system – Describe the life process– Describe the mechanism of homeostasis

Why are we here?Why are we here?

• To learn about human anatomy and physiology.

• Before we begin, we’ve got to figure a few things out:

1. What’s a human?2. What’s anatomy?3. What’s physiology?

What are humans?What are humans?• Organisms are classified as

human because they are:– Animals– Vertebrates

• Possess backbones

– Mammals• Possess:

– Mammary glands– Hair– Endothermy (i.e., we generate heat internally)– Heterodonty (i.e., we have teeth w/ different

shapes and functions)– 3 middle ear bones.

What are What are humans?humans?

– Primates• Possess:

– Opposable thumbs (can you touch your pinky with your thumb?). What advantage does this confer?

– 2 clavicles (collarbones)– Only 2 mammary glands. Why only 2?

(Think about how many kids a woman normally gives birth to.)

– Forward facing eyes with stereoscopic vision (for depth perception)

– Hominids • Bipedal (walk on 2 legs)• Possess a large brain size/body size ratio

• What is anatomy?– Anatomy is defined as the study of…

• Structure refers to the shapes, sizes, and characteristics of the components of the human body.

• The word anatomy comes from 2 words:– Ana which means “up or apart”– Tomos which means “to cut”

Why these two words????

Types of AnatomyTypes of Anatomy• We can divide our study of structure into 2

parts:• Study of stuff seen by the naked eye (Gross

Anatomy).

• Study of stuff seen ONLY with the microscope (Microanatomy).– We can divide microanatomy into:

» Histology – study of tissues» Cytology – study of individual cells.

PhysiologyPhysiology• Physiology is defined as

the study of function – so human physiology attempts to explain how and why humans function.

• Physiology is where we figure out how stuff works.

• How do muscles contract?

• How do we run?• How does our heart

beat?

Some Important Some Important ThemesThemes

1. Biology is hierarchical with each level building on the level below it.

2. Each level of biological structure has emergent properties.

3. Cells are an organism’s basic unit of structure and function.

4. Structure and function are correlated at all levels of biological organization!!!!!!!!

5. Regulatory mechanisms ensure a dynamic balance in living systems.

Levels of Levels of StructureStructure

• In order to understand how something is built and how something works, you must look at all of its components and analyze them both individually and together.

• In doing these collective and separate analyses, you must examine things at multiple structural levels, i.e., one must break them down from large to small – this is called reductionism

• An organism (such as a human being) may be broken down as illustrated on the left.

Organelle

Cell

Tissue

Organ

Organ System

Organism

Levels of Levels of StructureStructure

• The basic unit of life is the cell.• All living organisms are composed of one or

more cells.• The human body contains about 100 trillion

cells.• There are about 200 different types of cells in

the human body.• The different types of cells have different

features but for the most part, all cells are made up of organelles and various macromolecules (e.g., proteins, lipids, carbohydrates and nucleic acids).

• Organelles themselves are made of these macromolecules and macromolecules are polymers of smaller molecules which consist of atoms of various chemical elements.

A Prototypical CellA Prototypical Cell

Important Organelles Important Organelles • Plasma Membrane → Separates the cell exterior

from the cell interior (cytoplasm).• Nucleus → Membrane bound structure that

contains deoxyribonucleic acid (DNA) which is the set of instructions for the synthesis of all the body’s proteins.– CAN YOU SEE THE NUCLEUS AND THE

PLASMA MEMBRANE IN THE CELL TO THE RIGHT?

• Mitochondria → Structure bound by a double membrane and the site at which the energy stored in sugars and other organic molecules is transferred to ATP, the chemical which acts as the “currency” for energy in the cell.

• Ribosomes → Not bound by a membrane. Sites of protein synthesis. May be free – floating in the cytoplasm – or bound to the endoplasmic reticulum.

Are the 2 pictures on this page to the same scale? How do you know?

Important OrganellesImportant Organelles• Rough Endoplasmic Reticulum

→ Membranous set of tubes with ribosomes studded along its surface. Site of the synthesis of proteins that are destined to be exported from the cell.

• Smooth Endoplasmic Reticulum → ER w/o the attached ribosomes. Site of cellular lipid synthesis, among other things.

• Golgi Apparatus → Membrane bound organelle responsible for determining the direction of proteins synthesized in the rough ER.

• Lysosomes → Membrane bound organelle that houses digestive enzymes that can be used to break down ingested toxins or worn out cell parts.

More Levels of StructureMore Levels of Structure• Similar cells and cell

products come together to form tissues.

• A structure made of 2 or more tissue types that perform a particular function is an organ.

• A group of organs with a unique collective function is an organ system. There are 11 of these in the human body.

Integumentary Integumentary SystemSystem

• Structures: - Skin, hair, sweat and oil glands

• Functions: - Forms the external body

covering- Protects deeper tissues from

injury- Involved in vitamin D synthesis- Prevents desiccation, heat

loss, and pathogen entry- Site of pain and pressure

receptors

Skeletal SystemSkeletal System• Structures:

– The 206 bones of the human body

• Functions:– Protects and supports body organs

• What characteristics might bone have that allows it to support and protect?

– Provides a framework that muscles can use to create movement

– Hemopoiesis (synthesis of blood cells)– Mineral storage

• Bone contains 99% of the body’s store of what mineral? (Hint you can get this mineral from drinking milk)

Muscular SystemMuscular System• Structures:

– The 600+ muscles of the body

• Functions:– Locomotion– Manipulation of the

environment– Maintaining posture– Thermogenesis

(generation of heat)

Nervous SystemNervous System• Structures:

– Brain, spinal cord, and peripheral nerves

• Functions:– Fast-acting control

system of the body– Monitoring of the

internal and external environment and responding (when necessary) by initiating muscular or glandular activity

Endocrine Endocrine SystemSystem

• Structures:– Hormone-secreting glands

• Pituitary, Thyroid, Thymus, Pineal, Parathyroid, Adrenal, Pancreas, Small Intestine, Stomach, Testes, Ovaries, Kidneys, Heart

• Functions:– Long-term control system

of the body– Regulates growth,

reproduction, and nutrient use among other things.

Cardiovascular SystemCardiovascular System

• Structures: – Heart, Blood vessels

(arteries, veins, and capillaries)

• Functions:– The heart pumps blood thru

the blood vessels.– Blood provides the transport

medium for nutrients (glucose, amino acids, lipids), gases (O2, CO2), wastes (urea, creatinine), signaling molecules (hormones), and heat.

Lymphatic/Lymphatic/ImmuneImmune System System

• Structures:– Lymphatic vessels, Lymph nodes,

Spleen, Thymus, Red bone marrow

• Functions:– Returning “leaked” fluid back to

the bloodstream, – Disposal of debris– Attacking and resisting foreign

invaders (pathogens i.e., disease-causing organisms)

Respiratory SystemRespiratory System• Structures:

– Nasal cavity, pharynx, trachea, bronchi, lungs

• Functions:– Constantly supply

the blood with O2, and remove CO2

– Regulate blood pH

Digestive Digestive SystemSystem

• Structures:– Oral cavity, esophagus, stomach, small

intestine, large intestine, rectum, salivary glands, pancreas, liver, gallbladder

• Functions:– Ingestion and subsequent breakdown of

food into absorbable units that will enter the blood for distribution to the body’s cells

Urinary SystemUrinary System

• Structures:– Kidneys, ureters,

urinary bladder,urethra

• Functions:– Removal of

nitrogenous wastes– Regulation of body’s

levels of water, electrolytes, and acidity

Reproductive SystemReproductive System

• Structures:– Male:

• Testes, scrotum, epididymis, vas deferens, urethra, prostate gland, seminal vesicles, penis

– Female:• Ovary, uterine tube,

uterus, cervix, vagina, mammary glands

• Functions:– Production of offspring

Why Are Levels of Structure Why Are Levels of Structure Important?Important?

• In this class, we’ll study all levels and see how they work together to create structures and allow them to function.

• In essence, the combination of these different yet connected levels allows life to proceed.

• But we must also be aware of emergent properties. – Things are often much more than simply a sum of their

parts.– Consider a hammer which is made of a head and a handle.

Either piece by itself is of little use to drive a nail – but put together, they perform the task quite easily.

– Or consider table salt – sodium chloride (NaCl). By themselves, chlorine is a poisonous gas and sodium an explosive metal. But when bound together, they create something much, much different.

We must be aware of emergent properties as well as reducing structures to their component parts.

Can Anatomy & Physiology Be Can Anatomy & Physiology Be Separated?Separated?

• NOOOOOOO!!!!! Absolutely not!• Structure and function are

undeniably connected. We cannot divorce them.

• What do we mean by this?– Can you eat soup with a fork?– Find 2 everyday items and determine

whether/how their structure (anatomy) relates to their function (physiology)

When you consider the structure of an organ, cell, or anything for that matter you must also consider its function!

Stayin’ AliveStayin’ Alive

• Your body has about 100 trillion cells in it.

• For your life to NOT end abruptly, these cells need to have the correct amount of:

• Oxygen • Nutrients • Waste removal• Heat• Ions (sodium, calcium, etc.)• Lots of other stuff

The Cell’s EnvironmentThe Cell’s Environment

• In order to keep the right amount of stuff in the cell, we’ve got to make sure that all the fluid surrounding our cells (i.e., the extracellular fluid) has the right assortment of nutrients, ions, etc.

• We keep both our cells and the fluid surrounding our cells in a dynamically stable environment via a process called HOMEOSTASIS.

HomeostasisHomeostasis• Defined as the body’s ability to maintain

stable internal conditions in spite of the changing external conditions.

• We just said that our body needs to have the right amount of stuff (i.e., temperature, blood [glucose], pH etc.) at all times in order to function properly.

• First, let’s refer to all this stuff as “different variables”

Note: the brackets surrounding the word glucose in the above paragraph mean “concentration of glucose,” i.e., how much glucose is dissolved in a particular fluid (blood in this case)

Let’s use a Let’s use a thermostat as an thermostat as an

exampleexample• In order to keep the temperature in my house

at the right level, the thermostat must first measure the current temperature in the house.

• After the thermostat measures the temperature, it compares the current value to a preset standard value. – If there is no difference then there’s nothing to do.– However, if it’s too hot or too cold, the thermostat

has to send a signal to the furnace or air conditioner to change the temperature of the house so that it equals the standard value.

Let’s clarify some stuff.Let’s clarify some stuff.• In the previous example we had a:

1. Variable temperature2. Measuring implement thermostat3. Control center also the thermostat4. A preset or standard value for the variable5. Effectors the air conditioner and furnace

• Similar situations arise in the human body where there are lots of variables that we want to maintain at certain precise levels

Blood Blood PressurePressure

• BP is a variable that we’ve got to maintain at a certain level

• We have sensory receptors that measure the BP in the body. They’re located in the aorta (the big blood vessel coming out of the heart) and in the carotid arteries (the large vessels that bring blood to the brain).

• These pressure receptors measure BP and then send the info (we can call this input) to a control center in the brain – the particular BP control center is in the medulla oblongata of the brain

Blood PressureBlood Pressure

• We call the connection btwn the receptor and the control center the afferent pathway.

• In the control center, the input BP is compared with a set value.

• If there is a difference between the current BP value and the reference BP value then we’ve got an error.

• And we’ve got to fix that error!

Blood PressureBlood Pressure• The control center will signal

effector organs – such as the heart in this case – to alter their activity. This process is called output.

• The connection between the control center and the effector organ is called the efferent pathway.

Blood PressureBlood Pressure• Suppose the current BP is too high.• The effector must act in a way to decrease

it – so the medulla oblongata (the control center) would signal the heart to decrease the force and rate of its contractions; this would decrease BP.

• Notice that the original stimulus was an INcrease in BP and the body’s response was to act so as to DEcrease BP.

• The stimulus is opposite the response!

Negative FeedbackNegative Feedback• B/c the movement of a variable in

one direction causes the body to enact processes that cause the variable to move in the opposite direction (so as to return the value to the correct level) – we call it negative feedback

• Let’s look at BP again:

Increased BP

Sensed by pressure receptors in aortic arch and carotid sinus

Input sent via afferent pathway to medulla oblongata

Current BP compared with set point and error signal generated

Output sent along efferent pathway to heart and blood vessels

Heart rate & force of contraction decrease

Blood vessel diameter increases

BP DECREASES

Why is Why is Negative Negative FeedbackFeedback so common in so common in

the body?the body?• Think about it! Every time a variable

starts changing too much, we’ve got to bring it back to normal. We’ve got to counteract its change.

• THAT’S NEGATIVE FEEDBACK

• Other examples you will encounter:– Maintenance of blood [Ca2+], blood

[Glucose], blood pH, and many others

When does a negative feedback process end?

THINK ABOUT IT!

• A negative feedback process begins when a particular variable leaves its homeostatic range.

• The process ends when that variable is back within its normal range.

• Negative feedback processes (or loops) are self-terminating.

MAKE SURE YOU UNDERSTAND WHY!

Homeostasis is Homeostasis is Important!Important!

• Most of the physiological processes that occur in your body are designed to maintain homeostasis. – ALWAYS KEEP THIS IN MIND!

• Question: Does the magnitude (i.e., size) of the error signal influence the magnitude of the response?

• Just to recap, let’s look at a couple more figures!

HomeostaHomeostasis is sis is

DYNAMIC!DYNAMIC!

What this means is that the homeostatic variables are NOT kept rigidly fixed upon a single value. They are kept within a certain range, and when they exit that range – that’s when negative feedback loops turn on to bring them back.

Is your body temperature always exactly 98.6F?

What about Positive What about Positive Feedback?Feedback?

• Positive feedback occurs when the response amplifies or magnifies the stimulus that produced it.

• In other words, a variable is altered and then the body’s response alters that variable even more in the same direction.

• How does this differ from negative feedback?

• Which do you suppose is more common in the body: positive or negative feedback?

Positive Positive FeedbackFeedbackin in ChildbirthChildbirth

Positive Positive

FeedbacFeedbackkin Blood in Blood ClottingClotting

Dangerous Positive Dangerous Positive FeedbackFeedback

Rise in body temperature

Increase in body metabolism

Increase in body heat production

What stops a positive What stops a positive feedback loop?feedback loop?

Water, water Water, water everywhere!everywhere!• About 60% of the human body is water• 2/3 of this water is found within your

cells so we refer to it as intracellular fluid (ICF)

• The other 1/3 is outside your cells so we call it extracellular fluid (ECF)

• The 2 main types of ECF are:1. The fluid that surrounds the cells – the

tissue fluid or interstitial fluid2. Blood!

• Minor types of ECF include cerebrospinal fluid and intraocular fluid

Related Fields of StudyRelated Fields of Study• Obviously, anatomy and physiology

come under the rubric of biology – the study of life.

• An incredibly integral field is pathology – the study of disease. – Why is pathology so important in

learning A&P?

• Another super important field is embryology, the study of how a single zygote (i.e., a fertilized egg) turns into a fully-fledged human being with trillions of cells. – Why is embryology so important to A&P?