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Lateral view of the human skull

This image shows a side view of the human skull. The major parts of the cell are labeled.

Chapter objectives

After studying this chapter, you will be able to:

  • Describe the functions of the skeletal system and define its two major subdivisions
  • Identify the bones and bony structures of the skull, the cranial suture lines, the cranial fossae, and the openings in the skull
  • Discuss the vertebral column and regional variations in its bony components and curvatures
  • Describe the components of the thoracic cage
  • Discuss the embryonic development of the axial skeleton

The skeletal system forms the rigid internal framework of the body. It consists of the bones, cartilages, and ligaments. Bones support the weight of the body, allow for body movements, and protect internal organs. Cartilage provides flexible strength and support for body structures such as the thoracic cage, the external ear, and the trachea and larynx. At joints of the body, cartilage can also unite adjacent bones or provide cushioning between them. Ligaments are the strong connective tissue bands that hold the bones at a moveable joint together and serve to prevent excessive movements of the joint that would result in injury. Providing movement of the skeleton are the muscles of the body, which are firmly attached to the skeleton via connective tissue structures called tendons. As muscles contract, they pull on the bones to produce movements of the body. Thus, without a skeleton, you would not be able to stand, run, or even feed yourself!

Each bone of the body serves a particular function, and therefore bones vary in size, shape, and strength based on these functions. For example, the bones of the lower back and lower limb are thick and strong to support your body weight. Similarly, the size of a bony landmark that serves as a muscle attachment site on an individual bone is related to the strength of this muscle. Muscles can apply very strong pulling forces to the bones of the skeleton. To resist these forces, bones have enlarged bony landmarks at sites where powerful muscles attach. This means that not only the size of a bone, but also its shape, is related to its function. For this reason, the identification of bony landmarks is important during your study of the skeletal system.

Bones are also dynamic organs that can modify their strength and thickness in response to changes in muscle strength or body weight. Thus, muscle attachment sites on bones will thicken if you begin a workout program that increases muscle strength. Similarly, the walls of weight-bearing bones will thicken if you gain body weight or begin pounding the pavement as part of a new running regimen. In contrast, a reduction in muscle strength or body weight will cause bones to become thinner. This may happen during a prolonged hospital stay, following limb immobilization in a cast, or going into the weightlessness of outer space. Even a change in diet, such as eating only soft food due to the loss of teeth, will result in a noticeable decrease in the size and thickness of the jaw bones.

Questions & Answers

write short notes on ligaments,curves and moverment of vertebral column.
mutesi Reply
what is the Analysis
ROHIT Reply
what is Anatomy
ROHIT Reply
Cutting Up
Nonie
it's a organs and bouns reading
AJITH
Cutting Up
Nonie
what
AJITH
Cutting Up
Nonie
to dissect
Nonie
what usually cause blood pressurae
Abdullateef Reply
too much salt in the diet
Abuusu
older age
Abuusu
Even family history of high blood pressure
Abuusu
yes
Yaqub
too much salt in the diet
Yaqub
stress is the leading factor
Richard
smoking and too much alcohol consumption
Annu
obesity can also cause hypertension
Yaqub
high temperature of the body high salt of the body
Drs
how does the temperature affect the blood pressure?
Chidiebere
sex
Onavwie
What sex.?
Arshad
Male
Vikas
i mearnt gender,there's increased blood pressure in male than female
Onavwie
Why
Vikas
guys, read the question, involuntary pumping of heart causes the blood pressure in the arteries, he has not asked about high or low BP.
Jess
explain the cellular mechanism that produces tetanus and summation
Jenica Reply
epithelial cells polerity
jitendra Reply
tissues
Deepak
demonstrate the fluid replacement in the body
John Reply
the red blood cells is in the long bones or flat bones?
isbii
as age increases, the bone elongates .. will the joint vanish?
Sushruth Reply
what is anatomy?
Ivy Reply
structure
Allonda
discuss the organization of the body
Mwila Reply
explain the cellular mechanism that produces tetanus and summation
Chayanne Reply
explain why the muscle doesn't respond to low stimulus voltages
Chayanne
how would muscle contractions be affected if skeletal muscle fibers did have T - tubules?
Chayanne
tetanus is a disease caused by a bacteria causing rigidity and spasms of volutary muscles.. there is a prolonged construction of muscles caused by repeated stimuli
Marcus
muscles follow the "all or none law" when it comes to reponse to stimuli... muscle construction would have been affected because the T tubules are the conducting tracts that transport the or move the action potential in deporalizing the other parts of cell hence the muscle wont act as a single cell
Marcus
Skeletal muscle fibers do have t tubules that's how action potential propagates to spread throughout the muscle. Tetanus production is a phenomenon which is better explained in time rather then cellularly. Action potentials either separated in time or space are summated on the muscle and
Vikas
When the stimulus frequency hits more than 25 the individual twitches from the fibers summate and the muscle as a whole contracts. Cellulary, a good amount of calcium needs to be accumulated as is done by twitches adding together.
Vikas
what is the names of tarsus?
Fathia Reply
the region of the foot containing the seven tarsal bones.
Manja
the tarsal bones
Marcus
how the valves keep the blood moving in one direction?
Nonie Reply
They open and close during blood circulation,
Denis
Then valve open labb sound and valve close dabb sound
HARDIK
The valves for example the semilunar valves act to prevent back flow of blood from arteries to ventricles during ventricular diastole and help to maintain pressure on the major arteries .The aortic semilunar valve separate the left ventricle from opening of the aorta.
Denis
thank you
Nonie
😷
HARDIK
hi
Shakir
hello
Manja
Yes
kannan
what are estrogen and progesterone ? and their functions
Emmanuel
it's a body hormones and this is spread by women and it's can help to reproduction system...
HARDIK
yhe I also wana know
Lemasyanji
can we introduce ourselves and share contact?
Emmanuel
🤔
HARDIK
thanks
Emmanuel
i want ti study medicine.. what are the main course?
Emmanuel
Progesterone helps to maintain the endometrium wall which is later shed out of the body during the menstrual cycle
Smisha
Estrogen is another ovarian hormone which helps the primary follicle to develop into graafian follicle and cause ovulation
Smisha
what is decstro cardiac
priyanshi
Right sided heart in a guy
Vikas
Dextrocardia is a condition where the. heart lies in the right side of the thorax instead of the left and it occurs when the heart loops to the left instead of the right.
Idoko
hii
Vikas
can any talk me a scope of anatomy and physiology
Vikas
please
Vikas
It has valves that OPEN and close during circulation
xiao
What does the Thyroid gland means
Solomon Reply
It's a gland in your neck produces thyroid hormone maintains body metabolism
Vikas
how many joints are in the human foot?
Roghayeh Reply
I believe that is 33 joints
Ana
26 bones and 33 joints.
Amin
thank u.
Roghayeh
thanks
antouman

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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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