Skelatal System

Question 1

What is the intra-membranous ossification and give examples

Answer 1

a- Intra-membranous ossification: e.g. clavicle and skull cap. The bones develop directly from CT membrane (mesenchyme). It begins at one or more centers of ossification.

Question 2

What is intro cartilaginous ossification?

Answer 2

b- Intra-cartilaginous ossification: e.g. in long bones, vertebrae, ribs and base of skull. The mesenchyme is changed at first into a cartilage model, and then the cartilage is dissolved and disappears, and in its place is changed into bone.

Question 3

When are long bones located? (Site)

Answer 3

Upper and lower limbs

Question 4

What is the structure of long bones

Answer 4

[A] Long bones

Structure: two ends (epiphyses) and a shaft (diaphysis) in between.

•Epiphysis: it is the expanded upper and lower ends of the long bone. It is used for articulation and its articular surface is covered with a layer of articular hyaline cartilage.

• Diaphysis (Shaft):

A tube of compact bone with a central medullary cavity lined with endosteum and is filled with bone marrow (soft vascular tissue).

■The shaft is covered with fibrous sheath called periosteum.

The long bones increase in width from periosteum.

■In the growing long bones, the epiphysis and the diaphysis are separated by a disc of hyaline cartilage called epiphyseal cartilage which is responsible for the growth in length.

• Metaphysis: lies in the upper and lower parts of the long bone just beneath the epiphyseal cartilage. It is the most active part of long bone.

Question 5

Describe the diaphysis?

Answer 5

• Diaphysis (Shaft):

A tube of compact bone with a central medullary cavity lined with endosteum and is filled with bone marrow (soft vascular tissue).

■The shaft is covered with fibrous sheath called periosteum.

The long bones increase in width from periosteum.

■In the growing long bones, the epiphysis and the diaphysis are separated by a disc of hyaline cartilage called epiphyseal cartilage which is responsible for the growth in length.

Question 6

Functions of Skeleton:

Answer 6

a. Gives the specific shape to the body.

b. Provides the central axis of the body.

C. Protects the vital organs: the skull protects the brain, and thoracic cage protects the heart and lungs.

d. Provides surface area for muscular attachment.

e. Transmits and supports the body weight

f. Forms the joints

g. Forms the blood elements in the bone marrow.

h. Stores calcium salts.

Question 7

What are Pneumatic Bones:

Answer 7

Bones containing air
Site: Skull bones mainly those surrounding the nose (e.g. maxillary and frontal bones), so the air cavities are called paranasal sinuses.

Structure: the bone may contain one air cavity (maxillary sinus) or multiple small air cells (mastoid air cells).

Question 8

Describe the Arterial supply of bones

Answer 8

Nutrient artery supplies 2/3 of the thickness of the shaft and the bone marrow.it enters the middle of the shaft and runs away from the growing end.it divides into two branches

Periosteal artery in the periosteum supplies 1/3 of the shaft

Metaphysical artery supply the metaphysics but after ossification of the
Epiphyseal plate it anastomose with the nutrient-artery.

Epiphysial artery supply the epiphysis but after ossification of the
Epiphyseal plate it anastomose with the nutrient-artery.

Question 9

What are the properties of cartilage?

Answer 9

It is rubbery type of CT
Tough and resilient
No blood vessels nerves or lymphatics
Consist of nature cartilage cells, matrix fibers
Resists compression
Growth by multiplication

Question 10

What are types of cartilage?

Answer 10

1) hyaline 2) white fiber cartilage 3) yellow elastic fiber cartilage

Question 11

What are the characteristics and site of hyaline cartilage?

Answer 11

Most widespread in human body
Sites: 1) developing bones in fetus
2) epiphyseal plates
3) particular cartilage in joints
4) the larynx and tracheal rings
5) costal cartilage and xiphoid in sternum

Question 12

What are the characteristics and site of white fiber cartilage?

Answer 12

Opaque because it is rich in collagen bundles _ few cartilage cells
Sites → invertebrate disc

Question 13

What are the characteristics and site of yellow fiber cartilage?

Answer 13

Yellow because it is rich in yellow elastic fibers _ cartilage cells are abundant
Sites → tip of nose, auricle of the ear, epiglottis of the larynx

Question 14

What are the types of bones?

Answer 14

1) long bones 2) short bones 3) flat bones 4) pneumatic bones 5) irregular bones 6) sesamoid bones

Question 15

What are the positions of bones in the body?

Answer 15

Axial: skull, mandible hyoid, ribs and vertebrae sternum
Appendicular: upper and lower limbs

Question 16

Site of short bones?

Answer 16

Carpal bones in hand and tarsal bones in foot

Question 17

Site of flat bones?

Answer 17

Skull cap and ribs

Question 18

Site of pneumatic bones?

Answer 18

Maxillary and frontal bones

Question 19

Site of irregular bones?

Answer 19

Vertebrae

Question 20

Site of sesamoid?

Answer 20

Patella (kneejoint)

Question 21

What is the function of pneumatic bones?

Answer 21

Functions:

1. They decrease the weight of skull.
2. They lead to resonance of voice.
3. They have a highly vascular mucosa to warm the inspired air.

Question 22

How do long bones increase in length?

Answer 22

From the epiphysical plates

Question 23

How do long bones increase in width

Answer 23

From osteoblasts in the inner layer of the periosteum