L10 The Muscle Tissue: Smooth Muscle

Question 1

What are the 3 types of muscle tissue

Answer 1

Skeletal(voluntary)
Cardiac(involuntary)
Smooth(involuntary)

Question 2

Describe the smooth muscle in terms of:
Site
Shape
Nucleus 
Sarcoplasm

Answer 2

Site: wall of visceral organs such as blood vessels, git tube,urinary tract,respiratory passages
Lm features:
Shape: in LS smooth muscle fibers are fusiform elongated cells that taper at either ends
In TS cells appear rounded with diff diameters according to cut section

Nucleus: single and central oval nucleus housing 2 or more nucleoli
During contraction: corkscrew appearance

Sarcoplasm: homogenous eosinophilic on staining with h and e

Question 3

What is smooth muscle surrounded by

Answer 3

Each smooth muscle is surrounded by an external lamina which invariably separates the sarcolemma of contiguous muscle cells

Question 4

What is embedded in external lamina of smooth ms and what is their function

Answer 4

Embedded in external lamina are numerous reticular fibers which appear to envelope individual smooth muscle cells and function in harnessing the force of contraction

Question 5

What is the structural organization of smooth ms

Answer 5

1)in wall of visceral organs smooth ms are arranged in two perpendicular layers as in the digestive and urinary systems
This permits wave peristalsis

2)in each later smooth ms are arranged in same direction in an interdigitating pattern

Question 6

Describe the ultra structure of smooth ms

Answer 6

▪️Peri nuclear cytoplasm of smooth ms especially regions adj to the poles of the nucleus contain numerous mit,golgi app RER and SER and inclusions such as glycogen
▪️contractile myofilaments are arranged in bundles so that thin are at peripheral part and thick are at central region
▪️desmin intermediate filaments form a network to transmit contractile action between ms bundles
▪️dense bodies are formed of an anchoring protein that fixes one end of actin myofilaments and desmin

Question 7

What are the types of contractile myofilaments

Answer 7

Thin: actin and tropomyosin
Thick: myosin

Question 8

Why does sarcoplasm have smooth appearance under microscope

Answer 8

Due to bundles of myofilaments being oriented in diff directions thus lacking regular registration encountered in skeletal ms

Question 9

How is transmission of electrical activity

Generated in sarcolemma

Answer 9

Upon nervous simulation through caveolae as they are associated with profiles of SER to release stored ca ions in to sarcoplasm to initiate contraction

Question 10

Explain how the neural component can cause innervation

Answer 10

En passant type
Which occurs as axonal swelling that contain synaptic vesicles housing either norepinephrine for sympathetic innervation or acetylcholine for parasympathetic innervation

Question 11

How are smooth muscles connected and why

Answer 11

Gap junction

So as to transmit nerve impulses rapidly between cells

Question 12

How can smooth ms contract in response to hormonal stimulation

Answer 12

Oxytocin that acts on uterine smooth ms

Question 13

What are proteins that smooth ms can synthesize

Answer 13

Collagen elastin glycoasminoglycans

Proteoglycans and growth factors

Question 14

How do smooth ms response to stress

Answer 14

Smooth muscles retain their mitotic ability
During pregnancy uterus becomes thicker by both hypertrophy and hyperplasia by smooth ms cells
Injury defects may be due to mitosis by smooth ms or by differentiation of relatively undifferentiated pericytes