Smooth muscle

 

  
Smooth muscle microscope video

  Smooth muscle is also called plain or, involuntary muscle is found in the lower part of the esophagus.  It is also found in the large and small intestine, the respiratory tract below the bronchi.   It is found in the vagina, urethra, uterus, Fallopian tube, spleen salivary glands, artery and veins. It is made up of smooth muscle cell called myocyte which is spindle-shaped with a nucleus that is centrally placed. The myocyte is the muscle fiber. Its sarcoplasm has longitudinal striations which are indistinct but no transverse striations. The length of a smooth muscle cell or muscle fiber is about 15-500 m.

The smooth muscle cell contains myofibrils containing myofilaments actin and myosin disposed in a haphazard manner, hence the smooth appearance of the muscle under the microscope.   It has numerous mitochondria and sarcoplasmic reticulum.   It possesses yellow pigment granules.   Muscle fibers are attached to each other by a cement like substance.

Smooth muscle tend to have extracellular fibers such as collagenous, reticular and elastic fibers which represents its fibrous basis, while the myocyte is its cellular basis. Myocytes themselves secrete the proteins that form the fibers. Arrangements of the smooth muscle in various organs differ. This in most parts of the gut it is inner circular and outer longitudinal. In the stomach however the inner most fibers are disposed obliquely, while circular is intermediate and longitudinal is outermost. This arrangement favors peristalsis. Smooth muscles are innervated by the autonomic nervous system since they are involuntary and therefore autonomous. This system is divided into parasympathetic and sympathetic divisions.

 

 

Click here for practical, scan or tissue diagnosis  gross
histophysiology  histochemistry  histopathology  histopharmacology

  Electronic School of Medicine
Creator: Oluwole Ogunranti

 
        


Section of zone 49 of 66 zones of human oviduct at distal junctura. 1 mucosal fold 2 submucosa 3 inner longitudinal muscle fibers 4 circular muscle fibers 5 outer longitudinal muscle fibers 6 serosa. Arrow points to lamina propria.

 

 

 

 

 

 

 

 

 

 

 

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Introduction

Histology

   Smooth muscle

   Striated muscle

   Cardiac muscle

Embryology
Gross anatomy
Organ integration
Clinical anatomy

Quiz

Physiology

Smooth muscle      

Striated muscle      

Cardiac muscle      

Biochemistry

Pharmacology
Smooth muscle      

Striated muscle    

Cardiac muscle      

Chemical Pathology

Anatomical Pathology

Imaging

Medicine

Surgery

Main Subject Course Links

Anatomy Anesthesia Biochemistry Chemical pathology Community Health
Dermatology ENT Gynecology Hematology Imaging
Medicine Medical microbiology Obstetrics Ophthalmology Pathology
Pediatrics Pharmacology Physiology Psychiatry    Surgery/Orthopedics
eLab eOSCE eProcedures eInvestigations eSchool/Videopage
eOrgans eLocator Anatomy Museum eDissector eFractures
All diseases eClerking eTreatment eDoctor ePatient