Question

In this discussion, you will examine ways in which muscles can be weakened or strengthened.

Objectives

• Describe the gross and microscopic anatomy of skeletal muscle.
• Describe the anatomical differences between skeletal, smooth, and cardiac muscles.
• Explain the current concept of muscle contraction based on three factors: neuroelectrical, chemical, and energy sources.
• Define muscle tone.
• Compare isotonic and isometric contractions.

Step 1: Respond to the following:

In addition to experiencing disorders and diseases that can affect muscles, people can strengthen or weaken their muscles in various ways. Certain diseases, for example, can weaken muscles; in contrast, people can develop routines that strengthen their muscles.

• Describe two ways in which people can, perhaps unintentionally, weaken their muscles. What are two ways in which people can, intentionally or unintentionally, strengthen various muscles within their body?
• Search a reputable source to find an online article that discusses ways of strengthening muscles. Summarize the article in a sentence or two.
• Explain whether you agree or disagree with what the article suggests and why.

Answer 1

Gross structure of bone

Bone Tissue

Bones support and protect the body and its organs. They also produce various blood cells, store minerals, and provide support for mobility in conjunction with muscle. Bone is made of bone tissue, a type of dense connective tissue.

Bone (osseous) tissue is the structural and supportive connective tissue of the body that forms the rigid part of the bones that make up the skeleton. Overall, the bones of the body are an organ made up of bone tissue, bone marrow, blood vessels, epithelium, and nerves.

There are two types of bone tissue: cortical and cancellous bone. Cortical bone is compact bone, while cancellous bone is trabecular and spongy bone.

Cortical bone forms the extremely hard exterior while cancellous bone fills the interior. The tissues are biologically identical but differ in the arrangement of their microstructure.

Bone Cells

The following are the different types of bone cells:

Osteoblasts-involved in the creation and mineralisation of bone

Osteocytes and osteoclasts: These are involved in the reabsorption of bone tissue. The mineralized matrix of bone tissue has an organic component—mainly made of collagen—and an inorganic component of bone mineral made up of various salts.

Bone Types

There are different types of bone. These are:

Long bones

Short bones

Flat bones

Sesamoid bones

Irregular bones

Supply of Blood and Nerves to Bone

The blood and nerve supply to bones are carried in Haversian canals that run along the long axis of bones.

Blood is supplied to mature compact bone through the Haversian canal. Haversian canals are formed when individual lamellae form concentric rings around larger longitudinal canals (approx. 50 µm in diameter) within the bone tissue.

Haversian canals typically run parallel to the surface and along the long axis of the bone. The canals and the surrounding lamellae (8–15) are called a Haversian system or an osteon. A Haversian canal generally contains one or two capillaries and nerve fibers.

The Haversian canals also surround nerve cells throughout the bone and communicate with osteocytes in lacunae (spaces within the dense bone matrix that contain the living bone cells) through canaliculi. This unique arrangement is conducive to the storage of mineral salt deposits that give bone tissue its strength.

MICROSCOPIC

Bones are composed of bone matrix, which has both organic and inorganic components. Bone matrix is laid down by osteoblasts as collagen, also known as osteoid. Osteoid is hardened with inorganic salts, such as calcium and phosphate, and by the chemicals released from the osteoblasts through a process known as mineralization.

The basic microscopic unit of bone is an osteon (or Haversian system). Osteons are roughly cylindrical structures that can measure several millimeters long and around 0.2 mm in diameter.

Each osteon consists of a lamellae of compact bone tissue that surround a central canal (Haversian canal). The Haversian canal contains the bone’s blood supplies. The boundary of an osteon is called the cement line. Osteons can be arranged into woven bone or lamellar bone.