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By the end of this section, you will be able to:
  • Describe the location and position of the heart within the body cavity
  • Describe the internal and external anatomy of the heart
  • Relate the structure of the heart to its function as a pump
  • Compare systemic circulation to pulmonary circulation
  • Identify the veins and arteries of the coronary circulation system
  • Trace the pathway of oxygenated and deoxygenated blood thorough the chambers of the heart

The vital importance of the heart is obvious. If one assumes an average rate of contraction of 75 contractions per minute, a human heart would contract approximately 108,000 times in one day, more than 39 million times in one year, and nearly 3 billion times during a 75-year lifespan. Each of the major pumping chambers of the heart ejects approximately 70 mL blood per contraction in a resting adult. This would be equal to 5.25 liters of fluid per minute and approximately 14,000 liters per day. Over one year, that would equal 10,000,000 liters or 2.6 million gallons of blood sent through roughly 60,000 miles of vessels. In order to understand how that happens, it is necessary to understand the anatomy and physiology of the heart.

Location of the heart

The human heart is located within the thoracic cavity and is separated from the other structures by a tough membrane known as the pericardium, or pericardial sac.

Position of the heart in the thorax

This diagram shows the location of the heart in the thorax.
The heart is located within the thoracic cavity, medially between the lungs in the mediastinum. It is about the size of a fist, is broad at the top, and tapers toward the base.

Everyday connection

Cpr

The position of the heart in the torso between the vertebrae and sternum (see [link] for the position of the heart within the thorax) allows for individuals to apply an emergency technique known as cardiopulmonary resuscitation (CPR) if the heart of a patient should stop. By applying pressure with the flat portion of one hand on the sternum in the area between the line at T4 and T9 ( [link] ), it is possible to manually compress the blood within the heart enough to push some of the blood within it into the pulmonary and systemic circuits. This is particularly critical for the brain, as irreversible damage and death of neurons occur within minutes of loss of blood flow. Current standards call for compression of the chest at least 5 cm deep and at a rate of 100 compressions per minute, a rate equal to the beat in “Staying Alive,” recorded in 1977 by the Bee Gees. If you are unfamiliar with this song, a version is available on www.youtube.com. At this stage, the emphasis is on performing high-quality chest compressions, rather than providing artificial respiration. CPR is generally performed until the patient regains spontaneous contraction or is declared dead by an experienced healthcare professional.

When performed by untrained or overzealous individuals, CPR can result in broken ribs or a broken sternum, and can inflict additional severe damage on the patient. It is also possible, if the hands are placed too low on the sternum, to manually drive the xiphoid process into the liver, a consequence that may prove fatal for the patient. Proper training is essential. This proven life-sustaining technique is so valuable that virtually all medical personnel as well as concerned members of the public should be certified and routinely recertified in its application. CPR courses are offered at a variety of locations, including colleges, hospitals, the American Red Cross, and some commercial companies. They normally include practice of the compression technique on a mannequin.

Cpr technique

The top panel shows a schematic of a person performing CPR and demarcates the region in the chest where the compression must be performed. The bottom panel shows a photo of a person performing CPR on a dummy.
If the heart should stop, CPR can maintain the flow of blood until the heart resumes beating. By applying pressure to the sternum, the blood within the heart will be squeezed out of the heart and into the circulation. Proper positioning of the hands on the sternum to perform CPR would be between the lines at T4 and T9.

Questions & Answers

In the digestive system,what are nucleotides and what is their use
Leo Reply
what is the difference between kidney and liver
Raphael
what's an isomer
marybertiny Reply
is a chemical species with the same number and types of atoms as another chemical species but with distinct properties because rhe atoms are arranged into different chemical structures.
yaad
How are they important to anmals
Leo
immune system protect body from harmful foreign cells
Hira Reply
that's right some time when bacteria attached the body the immune system product
abdala
what is function of the body
Sarat Reply
Body funtion. Our bodies consist of a number of biological systems that carry out specific functions necessary for everyday living. The job of the circulatory system is to move blood, nutrients, oxygen, carbon dioxide, and hormones, around the body. It consists of the heart, blood, blood vessels,art
Sayed
what's the function of the lymphatic system
Samuel
what are tissue
Nkeng Reply
what are the difference type of connective tissue
Nkeng
Types of connective tissue 1. Loose connective tissue: a.Areolar connective tissue b.Adipose connective tissue 2. Dense (fibrous) connective tissue: I. Compact tissue a.White fibrous tissue ( tendon and sheath) b.Yellow elastic tissue (Ligament) II. Supporting connective tissue: types- 1. Cartilag
iti
2. Bone III. Fluid or liquid connective tissue: Blood lymph
iti
What is cytoplasm
Uyi Reply
what is cytoplasm
Morgan
a cytoplasm is a fluid found inside the cell membrane which contains dissolved minerals e.t.c.
Fortune
ok
Morgan
why is the the mitochondria known as the power house?
Fortune
The mitochondria is involved in releasing energy from food..this process is known as cellular respiration.
Sherice
ok
Fortune
what is Deoxyribonucleic Acid (DNA)?
Jackson
is a molecule composed of two chains.
Fortune
is a molecule composed of two chains that coil around each other to form a double helix carrying the genetics instructions used in growth,development e.t.c.
Fortune
Thanks
Jackson
structur of the heart
Munyah Reply
hi
Unimke
Hello
Mariam
miss Mariam u are welcome
Emmanuel
hello
wana
hii
Dein-aboh
hi
Wani
how
Renzo
hello every one
BOBO
hello
iti
hello
Hilmi
hello
Eshiemoghie
hi
Vaishnavi
what is mutation?
Oliver
Hi to everybody
Hussein
essay for photosynthesis
NiCho Reply
essay of the human body
NiCho
how do female menstrual uterus prepare for fertilisation?
Jackson
what is blood pressure
Sid Reply
to my understanding blood pressure is where u are shock with something emergency I think that can also course blood pressure
Badu
what is the meaning of extended family
Shellyann Reply
extended family is two are more nuclear family living together under one roof
Nordalee
what is genetic engineering
Ebot Reply
good day please what is a cell?
Colota Reply
cell is the basic unit of all living things/organism
Hassan
differenciate b/w cilia and flagellum
Abshira
Cilia: 1. They are smaller in number. 2. Cilia usually occur throughout or major part of the surface of a cell. 3. They beat oar like and in a co-ordinated rhythm 4. Cilia help in locomotion, feeding, circulation, etc.. 5. Example: Paramecium
iti
Flagella: 1. They are larger in size. ADVERTISEMENTS: 2. Flagella are commonly found at one end of the cell. 3. The flagella beat whip-like and independently. 4. Flagella help in locomotion. 5. Example: Euglena
iti
smallest structural and functional unit of an organism!
zidane
cell is the basic unit of all living things
Lukman
A cell is a basic unit of life
Badu
please I want to know the meaning of Tissues
Badu
hellooo here
Ebot
h2
Oliver
meaning of dispesing
Oliver
thnk u iti
Abshira
tissue is a group of identical cells having common origin
iti
what is the word? dispensing or dispersing...check the spelling of the word.
iti
dispersing
Oliver
Smaller in size not in number
Md
They are small in size and more in number
Md
Not identical but similar
Md
 cell is the smallest unit of life. Cellsare often called the "building blocks of life". The study of cells is called cellbiology. Cells consist of cytoplasm enclosed within a membrane, which contains many biomolecules such as proteins and nucleic acids.
Harun
hi
Vaishnavi
how are u doing
Emmanuel
this thing I don't know whether is an instruments use to measure pressure Sphygmomanometer is it true or not because in my formal school that's my master told me
Badu
dispersing means distribution or spreading
iti
sphygmomanometer is used for measuring blood pressure
iti
thanks
Oliver
mention the functions of mitochondria?
Oliver
mitochondria is the powerhouse of cell. it generates and stores energy in the form of ATP molecules in its oxysomes. it has its own DNA so its capable of self replicating and hence also called as semi autonomous organelle
iti
welcome
iti
explain briefly anatomy
Oliver
anatomy is thr study of internal structures and their organization as well as functions of living organisms
iti
OK thanky
Oliver
Yes
Hilmi
Good
Moses
welcome
iti
differenciate b/w red blood cell and whight blood cell
BOBO
d
Wani
what is homeostasis
alex Reply
the ability of an organism to maintain stable internal environment, even when the external environment changes
Bee
what's the function of the hypothalamus
Agyekum
what is homeostasis
Edward Reply
constant maintenance of internal body temperature
Agyekum
What is the function of the Pituitary Gland?
WeNdlovu
how can homeostasis be maintained?
alex
pituitary gland also known as the master gland secretes hormones which triggers other gland to secretes their hormones
Agyekum
what's the full meaning of DNA and RNA
Deborah Reply
DNA is Deoxyribonucleic acid and RNA means Ribonucleic acid
Christian

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Source:  OpenStax, Human biology. OpenStax CNX. Dec 01, 2015 Download for free at http://legacy.cnx.org/content/col11903/1.3
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