muscle tissue

1. SMOOTH MUSCLE
RAMYA.H.
1ST M.Sc.Food&
Nutrition

2. DISTRIBUTION
OFSMOOTH
MUSCLE
 Non-striated(plain) and involuntary.
 present in almost all the organs in the form of sheets, bundles or
sheaths around other tissues.
 Structures in which smooth muscle fibers are present:
1. Wall of organs like esophagus, stomach and intestine in the GIT.
2. Ducts of digestive glands.
3. Trachea, bronchial tube and alveolar ducts of respiratory tract.
4. Ureter, urinary bladder and urethra in excretory system.
5. Wall of the blood vessels in circulatory system.
6. Mammary glands, uterus, genital ducts, prostate gland and
scrotum in the reproductive system.
7. Iris and ciliary body of the eye.

4. FUNCTIONS
OFSMOOTH
MUSCLE
 In Cardiovascular system
Around the blood vessels regulate blood pressure and blood flow.
 In Respiratory system
Contraction and relaxation of smooth muscle of air passage regulate
inflow and outflow of air.
 In Digestive system
Helps in the movement of food substances, mixing it with digestive
juices and elimination of unwanted substances.
 In Renal system
Regulate renal blood flow and glomerular filtration. Propels urine
from kidneys to urinary bladder through ureter.
 In Reproductive system
In males, it facilitates the movement of sperms. In females, it
accelerates the movement of ovum into uterus through fallopian
tube.

5. STRUCTURE
OFSMOOTH
MUSCLE
 Fusiform or elongated cells
 2-5 microns in diameter & 50-200 microns in length
 Single and elongated nucleus, centrally placed
 Contractile proteins –actin, myosin and tropomyosin.
 thick and thin filaments-present, not arranged in orderly fashion
like skeletal muscle. Thick filaments formed by myosin. Thin
filaments formed by actin and tropomyosin.
 Dense bodies-formed by the protein desmin.Attached to thin
filaments. Scattered in sarcoplasm. Not arranged in straight line.
 Covering and tendons- covered by connective tissue.Tendons
absent.

6. TYPESOF
SMOOTH
MUSCLE
1. Single unit or visceral smooth muscle.
2. Multiunit smooth muscle.

7. SINGLEUNIT
SMOOTH
MUSCLE
 In an organ smooth muscle fibers functions as one unit.(all the
muscles fibers of an organ, contracts and relax together)
 Fibers have many interconnecting gap junctions (ions move
freely).Thus a functional syncytium is developed.
 Its presence is more common in the body than multiunit smooth
muscle.
 Fibers are arranged in sheets or bundles.
 Pace maker cells –present, which are self excitable. So,
spontaneous rhythmic contractions occur.
 Situation-small blood vessels, walls of hollow organs such as GIT,
urinary system, reproductive system, respiratory system.
 Control of action-myogenic

8. MULTIUNIT
SMOOTH
MUSCLE
 Individual fibers.
 Function independently.(contracts and relaxes on its own)
 No gap junctions, each muscle fiber is innervated by single nerve
ending.
 Outer membrane made up of glycoprotein(insulate and separate
the muscle fibers from one another)
 Control of action-neurogenic(stimulated by nerves of autonomic
nervous system)
 Pacemaker cells-absent. No spontaneous contractions.
 Situation-ciliary muscles of the eye, iris of the eye.