Histology: Histological Structure of Muscle Flashcards
What does the parenchyma of an organ consist of?
the tissue which:
- conducts the specific function of the organ
- usually comprises the bulk of the organ
What is the stroma of an organ?
Everything apart from the parenchyma:
- connective tissue,
- blood vessels,
- nerves,
- ducts.
What is the parenchyma of skeletal tissue?
muscle tissue
What is the stroma of skeletal muscle?
connective tissue, blood vessels and nerves.
What are “parenchyma” and “stroma” terms applicable to?
parenchymal organs only! cannot be applied to tuberal organs!
How can one classify tuberal organs?
lumen (inside)
When does differentiation continue in skeletal muscles?
after the fibers have been formed and have reached a functional state.
How can muscle fibers be differentiated?
- red muscle
- mixed muscle
- white muscle
What is the difference between red and white muscles?
- same structural composition
- different proportions of myoglobin and mitochondria
How are vertebral skeletal muscle fibers differentiated?
into red (type 1, slow twitch), and white (type 2) muscles
Explain type 1 muscle fibers? What is their different name?
type 1 = slow twitch = red muscle
- dense with capillaries
- rich in mitochondria
- rich in myoglobin
(giving the muscle its red colour)
- relatively more sarcoplasm
Explain type 2 muscle fibers? What is their different name?
type 2 = fast twitch = white muscle
- less dense in mitochondria
- less dense in myoglobin
What types of fibers develop high myoglobin concentrations?
fibers specialised for aerobic metabolism
How do type 1 fibers contract? speed? force required? fatigue?
slow twitch fibers contract for long periods of time, with little force. fatigue very slowly/never.
Which type of fibers have limited contractions?
type 1 fibers, slow twitch
State an example of slow twitch fibers?
- in the mouth
- breathing
work for an unlimited time
How do type 2 fibers contract? fatigue? speed? force required?
fast twitch fibers:
- contract quickly and powerfully,
- fatigue very rapidly
- sustain only short anaerobic bursts of activity before muscle contraction becomes painful
Why do small animals have pale coloured flesh?
major fast muscle type (type 2) predominates.
What is an important feature of muscle fibers?
transdifferentiation.
red muscle tissue <–> white muscle tissue
What is a “mixed muscle”?
a type of muscle which contains both white and red muscle fibers
most muscles in the organism
What are the names of the different connective tissue layers covering muscle?
1) endomysium
2) perimysium
3) epimysium
What holds together skeletal muscle?
connective tissue
What is the function of connective tissue in skeletal muscle fibers?
hold together the skeletal muscle fibers
What is the function of the endomysium?
surround individual fibers (cells not myofibril).
surrounding the group of tubes
What is the function of the perimysium?
surround a group of fibers to form a fascicle
fills the space between the grouped tubes (grouped by the endomysium)
What is the epimysium? What is its function?
- the epimysium is a dense connective tissue
- it surrounds the entire muscle
surrounds the grouped tubes (endo)+filling (+capillaries&nerves) (peri)
What is a “fascicle”?
a group of muscle fibers surrounded by a perimysium.
What does the perimysium contain?
a rich network of capillaries and nerves
Where are the capillaries and nerves located?
in the perimysium
What does the epimysium continue with?
the tendon
What is a tendon?
a cord like structure that attaches muscle to bone
What do tendons consist of?
- parallel bundles of collagen fibers
What type of tissue are tendons made out of?
dense regular connective tissue
What is situated between the parallel bundles of collagen fibers?
rows of fibroblasts called tendinocytes
What are tendinocytes?
rows of fibroblasts
Do tendinocytes contain high or few blood vessels?
very few blood vessels
What does the tendon connect to?
the epimysium of the muscle
What are tendons surrounded by?
a connective tissue capsule
What are the three connective tissues of tendons?
1) endotendineum
2) peritendineum
3) epitendineum
What does the endotendineum surround?
- groups of fibers surrounded by fibroblasts
What does the peritendineum surround?
fascicles
What does the epitendineum surround?
tendons
What type of connective tissue is the epitendineum?
dense irregular connective tissue
What type of connective tissue is the peritendineum?
loose connective tissue
What type of connective tissue is the endotendineum?
loose connective tissue
What is the difference between the endomysium, and the endotendineum?
endomysium: covers one fiber (fibers consist of a bunch of fused cells)
endotendineum: covers at least a few fibers (collagen fibers are too small)
What does loose connective tissue cover? difference between muscle and tendons.
- loose connective tissue can cover a muscle fiber: bunch of cells which are fused together
- loose connective tissue cannot cover a tendon fiber: small collagen fiber (too small!)
What is a tendon sheath? What is it lined by? What does it secrete?
a tube-like cavity lined with a synovial membrane that secretes viscous lubricating synovial fluid, covering regions of tendons at points of friction between moving structures.
What is a mesotendon?
a fold of synovial membrane connecting a tendon to its synovial sheath through which the blood vessels reach the tendon.
What connects the synovial sheath to the tendon, allowing for the attatchment of blood vessels?
the mesotendon
What is the tendon tube cavity lined by?
a synovial membrane
What is the synovial membrane composed of?
1) type A cells (macrophage-like cells): phagocytize unnecessary substances, antigen presenting cells
2) type B cells (fibroblast-like cells): produce lubricin and hyaluronin (lubricating purpose)
What is the synovial bursa? What is it lined with? What does it secrete? Where is it located? What is its purpose?
- saclike cavity
- lined with a synovial membrane
- secreates a *viscous lubricating synovial (bursal) fluid *
- interposed between tendons and bony prominences or at other points of friction between moving sutures
- reduces friction between bones and allows free movement
What is the structure of the synovial bursa?
round structure with everything inside
(lined with the synovial membrane)
ball completely filled with synovial liquid
What is the structure of the tendon sheath?
tubular like structure with the tendon located in the middle
(lined with the synovial membrane)
What is a “fascia”? What tissue is it composed of? What does it contain? How is it oriented?
- a structure of connective tissue that surrounds muscles, groups of muscles, blood vessels, and nerves (binding some structures together)
- a layer of dense regular connective tissue
- containing closely packed bundles of collagen fibers
- oriented in a wavy pattern parallel to the direction of pull
Is fascia flexible? What does that allow for?
fasciae are flexible sructures that are able to resist great unidirectional tension forces.
What does the fascia connect?
- 2 different muscles together
- blood vessels/nerves in between of muscles or inbetween of muscles and skin
What type of tissue is resistant from mechanical forces coming from various directions?
only dense irregular connective tissue
What type of tissue is resistant from mechanical forces coming from one directions?
dense regular connective tissue
