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By the end of this section, you will be able to:
  • Identify the primary functions of blood in transportation, defense, and maintenance of homeostasis
  • Name the fluid component of blood and the three major types of formed elements, and identify their relative proportions in a blood sample
  • Discuss the unique physical characteristics of blood
  • Identify the composition of blood plasma, including its most important solutes and plasma proteins

Recall that blood    is a connective tissue. Like all connective tissues, it is made up of cellular elements and an extracellular matrix. The cellular elements—referred to as the formed elements    —include red blood cells (RBCs)    , white blood cells (WBCs)    , and cell fragments called platelets    . The extracellular matrix, called plasma    , makes blood unique among connective tissues because it is fluid. This fluid, which is mostly water, perpetually suspends the formed elements and enables them to circulate throughout the body within the cardiovascular system.

Functions of blood

The primary function of blood is to deliver oxygen and nutrients to and remove wastes from body cells, but that is only the beginning of the story. The specific functions of blood also include defense, distribution of heat, and maintenance of homeostasis.

Transportation

Nutrients from the foods you eat are absorbed in the digestive tract. Most of these travel in the bloodstream directly to the liver, where they are processed and released back into the bloodstream for delivery to body cells. Oxygen from the air you breathe diffuses into the blood, which moves from the lungs to the heart, which then pumps it out to the rest of the body. Moreover, endocrine glands scattered throughout the body release their products, called hormones, into the bloodstream, which carries them to distant target cells. Blood also picks up cellular wastes and byproducts, and transports them to various organs for removal. For instance, blood moves carbon dioxide to the lungs for exhalation from the body, and various waste products are transported to the kidneys and liver for excretion from the body in the form of urine or bile.

Defense

Many types of WBCs protect the body from external threats, such as disease-causing bacteria that have entered the bloodstream in a wound. Other WBCs seek out and destroy internal threats, such as cells with mutated DNA that could multiply to become cancerous, or body cells infected with viruses.

When damage to the vessels results in bleeding, blood platelets and certain proteins dissolved in the plasma, the fluid portion of the blood, interact to block the ruptured areas of the blood vessels involved. This protects the body from further blood loss.

Maintenance of homeostasis

Recall that body temperature is regulated via a classic negative-feedback loop. If you were exercising on a warm day, your rising core body temperature would trigger several homeostatic mechanisms, including increased transport of blood from your core to your body periphery, which is typically cooler. As blood passes through the vessels of the skin, heat would be dissipated to the environment, and the blood returning to your body core would be cooler. In contrast, on a cold day, blood is diverted away from the skin to maintain a warmer body core. In extreme cases, this may result in frostbite.

Questions & Answers

what is systemic anatomy
Friday Reply
definition of anatomy and physiology
Kapil Reply
how is albino affected
Ujam Reply
what are the important stuff in the papillary layer
Ujam
Melanie's is responsible for the change in the color of the skin
Ujam
what happened when they are badly severed
Ujam
what happened when they are badly severed
Ujam
Examples of glial cells?
Nesh Reply
glial cell s help in the attractive foces of motion in the cellular network
Ujam
What is glial cell?
Esther
what is homeostasis
Laura Reply
homeostasis- The ability to maintain relatively stable internal conditions even though the outside world changes continuously. i,e, maintaining normal values in your body such as Adequate blood levels,blood pressure, heart activity and blood pressure.
Williams
thank you
Laura
Give atleast three reasons to study anatomy and physiology
George Reply
It helps to know about the body structure properly and administer proper care for the patient
Opeyemi
what's augmentin
Aphet Reply
augmentin is a type of combination antibiotic.
wintana
Can you explain to Heart anatomy in details please?
Handren Reply
definition of anatomy and physiology
Sardar Reply
Anatomy is the study structure of the body while physiology is the study of function of the body
Ayan
What is a dorsal cavity?
John Reply
Explain in detail mitosis and meiosis
sedeck Reply
What is Sodium Potassium Pump?
Mwamba Reply
The process of moving sodium and potassium ions across the cell membrance is an active transport process involving the hydrolysis of ATP to provide the necessary energy. It involves an enzyme referred to as Na+/K+-ATPase
USAMA
yes men.
Carlos
does it mean that there are two definitions of gross anatomy
Esther Reply
what is anatomy?
Hridy Reply
I think it's the study of the internal and external features of the body and its physical relationship between body parts
Esther
anatomy is the study of all the structure of body parts of living organisms
Kishan
to study the structure of human body parts
Sardar
anatomy is the study of human body
Meena
jaundice causes by when bilirubin blockage of bilary system
mahamed Reply
Yeah, when there is a blockage in the bilary system( bile ducts) which lead to obstruction of the bile pigments called bilirubin leading to a characteristically yellowish appearance of the eyes.
ibrahim
yes
mahamed
there are three main resons why bilirubin levels in the blood may rise: 1. pre-hepatic jaundice,2. hepatic jaundice, 3. post hepatic
mahamed

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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