Skeletal System Overview

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Questions and Answers

What type of bone is the ulna classified as?

Long

List two functions of the skeletal system.

Support of the body and protection of soft organs.

Describe the main difference between compact bone and cancellous bone.

Compact bone is hard and dense, while cancellous bone is spongy and consists of trabeculae with spaces.

How many named bones are there in the human adult skeleton?

206 Signup and view all the answers

What are the two principal divisions of the skeletal system?

Axial skeleton and appendicular skeleton. Signup and view all the answers

What are sesamoid bones, and where can they typically be found?

Sesamoid bones are small bones embedded within tendons, commonly found in areas such as the patella. Signup and view all the answers

Describe the composition of the diaphysis of a long bone.

The diaphysis consists of an outer layer of compact bone, which is covered by the periosteum, and contains an inner medullary cavity. Signup and view all the answers

What is the function of the periosteum in bone anatomy?

The periosteum serves as a protective fibrous connective tissue that provides attachment for muscles, tendons, and ligaments, as well as a source for blood supply. Signup and view all the answers

How does bone marrow change from birth to adulthood?

At birth, the bone marrow is entirely red, but during childhood, yellow marrow replaces red in distal long bones; in adults, only red marrow remains in spongy bones. Signup and view all the answers

What is the difference between membranous ossification and cartilaginous ossification?

Membranous ossification involves the development of bone from connective tissue membranes, while cartilaginous ossification involves the formation of bone from cartilage. Signup and view all the answers

What bones make up the shoulder girdle in the appendicular skeleton?

The shoulder girdle consists of the scapula and clavicle. Signup and view all the answers

List the regions of the vertebral column and the number of vertebrae in each region.

The vertebral column has cervical (7), thoracic (12), lumbar (5), sacrum (5 fused), and coccyx (4 fused) regions. Signup and view all the answers

How are the bones of the upper and lower limbs connected to the axial skeleton?

The upper limb connects via the shoulder girdle, and the lower limb connects via the pelvic girdle. Signup and view all the answers

What classification criteria are used to categorize bones by shape?

Bones are classified into long, short, flat, irregular, pneumatic, and sesamoid based on their shape. Signup and view all the answers

Give an example of a flat bone and describe its role.

An example of a flat bone is the sternum, which protects the thoracic organs and provides attachment for ribs. Signup and view all the answers

What bones constitute the pelvic girdle in the appendicular skeleton?

The pelvic girdle is made up of the hip bones. Signup and view all the answers

What is distinctive about pneumatic bones?

Pneumatic bones contain air spaces, which reduce their weight and contribute to respiratory function. Signup and view all the answers

How many phalanges are found in each finger, and how does this differ in the thumb?

Each finger has 3 phalanges, while the thumb has 2 phalanges. Signup and view all the answers

Study Notes

Learning Outcomes

Students will be able to describe the divisions of the skeletal system, types of bones, structure of a long bone, and periosteum.

Case Scenario

A 22-year-old woman fractured the ulna in her left forearm.
The ulna is a long bone.

Functions of the Skeleton

Provides support for the body.
Gives the body its shape.
Protects soft organs.
Facilitates movement through skeletal muscle attachment.
Stores minerals and fats.
Produces blood cells.

Bone Composition

Bone is composed of bone cells, intercellular matrix, collagen fibers, inorganic salts, and minerals.

Classification of Bones

Compact bone: Hard and dense, forming the surface of bones.
Cancellous (spongy) bone: Present inside bones, consisting of trabeculae with spaces, resembling a sponge.

Divisions of the Skeletal System

Axial skeleton: Consists of bones around the body's longitudinal axis.
- Includes the skull, sternum, ribs, vertebral column, and hyoid bone.
Appendicular skeleton: Consists of bones of the upper and lower limbs (extremities), and the girdles connecting the limbs to the axial skeleton.

The Vertebral Column

Cervical region: Comprised of 7 cervical vertebrae (C1-C7).
Thoracic region: Comprised of 12 thoracic vertebrae (T1-T12).
Lumbar region: Comprised of 5 lumbar vertebrae (L1-L5).
Sacrum: Formed by the fusion of 5 sacral vertebrae (S1-S5).
Coccyx: Formed by the fusion of 4 coccygeal vertebrae.

The Appendicular Skeleton - Upper Limb

Shoulder girdle: Includes the scapula and clavicle, connecting the upper limb to the trunk at the sternoclavicular joint.
Arm: Contains the humerus.
Forearm: Contains the radius and ulna.
Hand: Contains 8 carpal bones, 5 metacarpals (numbered from one to five lateral to medial), and phalanges (3 in each finger except the thumb, which has 2).

The Appendicular Skeleton - Lower Limb

Pelvic girdle: Includes the hip bone, connecting the lower limb to the axial skeleton at the sacroiliac joint.
Thigh: Contains the femur.
Leg: Contains the tibia and fibula.
Foot: Contains 7 tarsal bones, 5 metatarsals (numbered from medial to lateral), and phalanges (3 in each toe except the big toe, which has 2).

Bone Shapes

Long bones: Examples include the humerus, femur, metacarpals, and phalanges.
Short bones: Examples include the carpal and tarsal bones.
Flat bones: Examples include the vault of the skull, ribs, sternum, and scapula.
Irregular bones: Varying shapes, examples include vertebrae and the hip bone.
Pneumatic bones: Contain air spaces, examples include the maxilla and frontal bones.
Sesamoid bones: Small, deposited in tendons, examples include the patella.

Structure of a Long Bone

Diaphysis: The shaft of the bone, formed of outer compact bone covered by periosteum and an inner medullary cavity.
Epiphysis: At both ends of the bone, formed of cancellous bone covered by compact bone. The articular surface is covered with hyaline cartilage.
Metaphysis: Part of the diaphysis close to the epiphysis.
Epiphyseal plates of cartilage: Cartilaginous discs between the epiphysis and diaphysis, facilitating growth of bone in length.

Periosteum

A fibrous connective tissue covering the bone, except at the site of articular cartilage.
Highly sensitive with a rich nerve supply.
Functions include:
- Attachment for muscles, tendons, and ligaments.
- Source of blood supply.
- Facilitates growth of bone in width.
- Aids in healing fractured bones.

Bone Marrow

Fatty vascular tissue filling the medullary cavity of long bones and the meshes of cancellous bone.
Involved in the formation of blood cells.
Form of bone marrow changes with age:
- At birth: Only red bone marrow fills all marrow cavities.
- During childhood: Yellow bone marrow replaces red marrow in the distal long bones.
- In Adults: Red bone marrow is only present in the meshes of spongy bone (skull, vertebrae, sternum, ribs, hip, upper end of the femur and humerus). The medullary cavity of all long bones contains only yellow bone marrow.

Bone Ossification

Membranous ossification: Bone develops from a membrane of connective tissue (mesenchymal ossification). Examples include the skull bones, shaft of the clavicle, and facial bones.
Cartilaginous ossification: Bone develops from cartilage.

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Description

This quiz covers the divisions of the skeletal system, types of bones, and the function of bones. Students will learn about the structure of long bones and the significance of bone composition. It also addresses the impacts of bone fractures through case scenarios.