1. Classification of Muscle
3 types—skeletal, cardiac, and smooth—based on the presence of striations, voluntary control, and cellular structure (nuclei, shape, and branching). Skeletal muscle is striated and voluntary; cardiac is striated and involuntary; smooth is non-striated and involuntary
Dr. Praveen Kurrey
08-05-2026
2. Types of Muscle
Muscle tissue histology reveals three distinct types—skeletal, cardiac, and smooth
Dr. Praveen Kurrey
08-05-2026
3. Muscle Classification
Dr. Praveen Kurrey
08-05-2026
4. Skeletal Muscle- T.S.
Skeletal Muscle (Striated, Voluntary)Cell Shape: Long, cylindrical, unbranched fibers. Nuclei: Multinucleated; nuclei are located peripherally, just under the sarcolemma. Striations: Visible light (I-band) and dark (A-band) bands due to organized sarcomeres (myofibrils). Connective Tissue: Organized into epimysium (whole muscle), perimysium (bundles/fascicles), and endomysium (individual fiber
Dr. Praveen Kurrey
08-05-2026
5. Skeletal Muscle-TS
Each muscle is a bundle of muscle fibres, each of which is a long multinucleated cell. Single mononucleated cells called myoblasts fuse together to form this multinucleated fibre (myotube) during development. This process also occurs to regenerate muscle fibres. The stripes come from the repeating sarcomeres.
Dr. Praveen Kurrey
08-05-2026
6. T.S. Of Skeletal Muscle
The dark purple nuclei can be seen on the edges of the muscle fibres. Sarcolemma - cellular membrane Terminal cisterna - extension of sarcolemma that stores calcium T-tubules - invaginations of sarcolemma that transfer action potentials to the inside of the muscle cell Sarcoplasm - cytoplasm Sarcomplasmic reticulum - modified endoplasmic reticulum Actin, myosin - contractile elements Sarcomere - functional unit (made of actin and myosin) Accessory proteins - titin, tropomodulin, alpha-actinin, desmin, nebulin, dystrophin, myomesin
Dr. Praveen Kurrey
08-05-2026
7. Skeletal Muscle Spindle
Tissue Sheaths --Endomysium - around single muscle fiber Perimysium - around multiple muscle fibers -> arranges them in fascicles Epimysium - around entire muscle
Dr. Praveen Kurrey
08-05-2026
8. T.S Skeletal Muscle
There are three types of connective tissue sheaths named for their location. Endomysium surrounds individual muscle fibers. It is made up of a delicate layer of reticular fibers and permits only small-diameter nerve fibers and capillaries, thus acting as a site of metabolic exchange.
Dr. Praveen Kurrey
08-05-2026
9. L.S. Skeletal Muscle
Perimysium is a slightly thicker layer of connective tissue consisting mainly of type I and III collagen and surrounds a group of fibers. This fiber group is referred to as a fascicle or bundle. Fascicles are the functional units of skeletal muscle tissue. The perimysium contains slightly larger blood vessels and nerve fibers than those traveling through endomysium
Dr. Praveen Kurrey
08-05-2026
10. Skeletal Muscle-TS
Epimysium surrounds the entire collection of fascicles making up an individual muscle. This dense connective tissue made up of mainly type I collagen contains the neurovascular supply to the muscle
Dr. Praveen Kurrey
08-05-2026
11. T.S Skeletal Muscle
The sarcomere is the functional unit of a skeletal muscle cell. Each sarcomere is about 2.5 micrometers in length. It is made up of multiple myosin and actin filaments oriented in parallel. The actin and myosin filaments overlap in certain places creating several bands and zones. A Z disc forms the boundary of the sarcomere on either side. Thin actin filaments project in either direction off of a Z disc but do not cross the entire length of the sarcomere. They are almost 8 nm in diameter and have tightly bound regulatory proteins called troponin and tropomyosin.
Dr. Praveen Kurrey
08-05-2026
12. Smooth Muscle
In transverse section (TS) (cross-section), smooth muscle appears as a packed, mosaic-like arrangement of circular or oval cells of varying diameters. Only cells cut through the central nucleus show a round, dense nucleus surrounded by cytoplasm; others appear as simple cytoplasmic rings without a nucleus.
Dr. Praveen Kurrey
08-05-2026
13. L.S. Smooth Muscle
Spindle-shaped, non-striated cells (3–10 µm thick, 20–200 µm long) with a single, central, cigar-shaped nucleus. In longitudinal sections, these fibers are aligned in parallel, showing a smooth, unbranched, and tapered structure that acts as involuntary, slow-contracting, and fatigue-resistant muscle.
Dr. Praveen Kurrey
08-05-2026
14. Smooth Muscle Histology
Cell Shape: Fusiform (spindle-shaped) with tapering ends. Nucleus: Single, centrally located, oval to cigar-shaped nucleus. Striations: Absent (unlike skeletal muscle), giving the muscle a "smooth" appearance.
Dr. Praveen Kurrey
08-05-2026
15. Histology of Smooth Muscle
Arrangement: Cells are packed tightly, connected by gap junctions that allow for synchronous contraction. Cytoplasm: Homogeneously eosinophilic (pink when stained with H&E) due to random, rather than arranged, contractile proteins (actin and myosin).
Dr. Praveen Kurrey
08-05-2026
16. Smooth Muscle - L.S.
LOCATIONS-- Visceral (Single-unit) Smooth Muscle: Found in the walls of hollow organs (e.g., stomach, intestines, uterus, bladder) and blood vessels. Multi-unit Smooth Muscle: Found in areas requiring fine control, such as the iris of the eye and walls of large arteries
Dr. Praveen Kurrey
08-05-2026
17. Smooth Muscle Histology
Function: These muscles are innervated by the autonomic nervous system to produce involuntary movements, such as peristalsis in the digestive tract and regulation of blood pressure in blood vessels
Dr. Praveen Kurrey
08-05-2026
18. L.S. of Smooth Muscle
The smooth muscle fibers group in branching bundles. As opposed to skeletal muscle fibers these bundles do not run strictly parallel and ordered but consist in a complex system. Cell Shape: Fusiform (spindle-shaped) with tapering ends. Nucleus: Single, centrally located, oval to cigar-shaped nucleus. Striations: Absent (unlike skeletal muscle), giving the muscle a "smooth" appearance.
Dr. Praveen Kurrey
08-05-2026