11 - Histology - Muscles and Nerves Flashcards
Types of muscle
1) Tissues - Skeletal, cardiac, smooth 2) Cells - Myoepithelial cells, myofibroblasts, pericytes
Size of skeletal muscle cells
10-100 micrometers in diameter, up to 30cm long
Arrangement of nuclei in skeletal muscle cells
Multinucleate, peripheral location of nuclei
Types of striated muscle
Cardiac, skeletal
Difference between myofibre and myofibril
Myofibre = whole muscle cell Myofibril = Contractile cytoskeletal unit within cell
Smooth muscle fibre shape
Fusiform 200-300 micrometers long by 5-6 micrometers wide
Histological appearance of skeletal muscle 1) 2)
1) Cross-section - peripheral nuclei 2) Longitudinal section - striated, peripheral nuclei, length of single cells
Histological appearance of cardiac muscle 1) 2)
1) Cross-section - Thick cells, central nuclei 2) Longitudinal - Central nuclei, striations, branching, shorter muscle cells than skeletal
Histological appearance of smooth muscle 1) 2) 3) 4)
1) Cross-section - Thin cels, central nuclei 2) Longitudinal - Central, elongated nuclei, branched, no striations. 3) Peripheral organelles 4) No myofibrils, t-tubules, sarcomeres
Which type of muscle is this?
Skeletal muscle
Which type of muscle is this?
Smooth muscle
Which type of muscle is this?
Cardiac muscle
Are myofibrils membrane-bound?
No
Which part of sarcomere anchors thin filaments?
Z-disc
What is the sarcoplasmic reticulum? 1) 2) 3)
1) Specialised ER 2) Network of membranes that store Ca2+ 3) Rich in Ca2+ ATPases that pump Ca2+ back into SR
T-tubules 1) 2)
1) Allow depolarisation across myocyte membrane to enter into cell, to SR. 2) Surround each myofibril, two T-tubules per sarcomere (where actin and myosin overlap)
Where do mitochondria sit in myocytes?
Lie in lines between myofibrils, in the same spaces that house T-tubules and SR membrane
Light microscope appearance of cardiac muscle 1) 2) 3) 4)
1) Many capillaries 2) Mono- or binucleate 3) Cells joined by intercalated discs 4) Cells form a network
Layout of intercalated discs in cardiac muscle 1) 2) 3)
1) Zig-zag pattern 2) When lying perpendicular to cells, made up of adherens junctions and desmosomes, to resist force 3) When lying parallel to cells, made up of gap junctions, to transmit depolarisation (electrically couple cells)
Type of muscle that lacks t-tubules, sarcomeres and myofibrils
Smooth muscle
Where does that connective tissue surrounding smooth muscle come from?
Smooth muscle cells generate connective tissue
Shape of contracted smooth muscle cells
Corkscrew
EM appearance of smooth muscle 1) 2)
1) Contains thick (myosin) and thin (actin) filaments 2) Dense bodies (made of same protein as Z-discs, anchor actin/thin filaments)
Smooth muscle contraction (Schematic)
SMOOTH MUSCLE CONTRACTION
Regeneration of muscle cells 1) 2) 3)
1) Limited regeneration of skeletal by satellite cells 2) No regeneration of cardiac 3) Good regeneration of smooth because of high plasticity
Myoepithelial cells
Surround some exocrine glands (EG: breast tissue). Squeeze out contents with actin/myosin contraction
Myofibroblasts
Involved in wound healing. Pull wound together, involved in scarring.
Cell type that contracts exocrine glands
Myoepithelial cells
Cell type that is involved in pulling a wond together
Myofibroblasts
Pericytes
Surround capillaries, contract to alter capillary blood flow. Contractile with actin/myosin
Cells that alter capillary tonicity
Pericytes
Layers of connective tissue in nerves 1) 2) 3)
1) Epineurium surrounds entire nerve 2) Perineurium wraps fasicles (bundles of neurons) 3) Endoneurium wraps individual nerves
Are myelinated axons visible in H&E stain?
No. Need a specialised stain to visualise myelination (EG: toluidine blue)
Are Schwann cell nuclei visible in H&E sections?
Yes
In a section, are nuclei visible in axons?
No. Nuclei of neurons are in cell body. Nuclei are probably from Schwann cells.
