Physiology
Basic Cellular
Regarding skeletal muscle, which of the following best describes a fascicle:
Answer:
Skeletal muscle is composed of numerous parallel, elongated, multinucleated cells called muscle fibres (or myofibres) each enclosed by endomysium, which are grouped together to form fascicles. Each fascicle is surrounded by perimysium.Skeletal Muscle Structure
Physiology / Basic Cellular / Skeletal Muscle Physiology
Last Updated: 26th July 2024
The skeletal muscles and skeleton function together as the musculoskeletal system.
Gross Structure
The connective tissue surrounding the whole muscle is called the epimysium. The connective tissue that extends beyond the body of the muscle eventually blends into a tendon, which is attached to bone or cartilage. Skeletal muscle is composed of numerous parallel, elongated, multinucleated cells called muscle fibres (or myofibres) each enclosed by endomysium, which are grouped together to form fascicles. Each fascicle is surrounded by perimysium.
Structure of Skeletal Muscle. (Image by Unknown, via Wikimedia Commons)
Muscle Fibres
Beneath the endomysium is the sarcolemma, an elastic sheath that projects into the cell as invaginations called T-tubules which wrap around the sarcomeres, particularly where the thin and thick filaments overlap. Each muscle fibre is composed of myofibrils separated by sarcoplasm and arranged in a parallel fashion along the long axis of the cell. Each myofibril is further subdivided into thick myosin and thin actin myofilaments which are responsible for the cross-striations.
Skeletal Muscle Fibre. (Image by Blausen.com staff (2014). "Medical gallery of Blausen Medical 2014". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. (Own work) [CC BY 3.0 , via Wikimedia Commons)
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
