Download Smooth muscles

NAME: MUHAMMED UMMSALMA MAJI
COURSE: ANA 203 (histology)
MATRIC NO.: 14/MHS01/081
LEVEL: 200
HISTOLOGY OF HAVERSIAN SYSTEM
A haversian system, also known as an Osteon, is a series of concentric
circles, called Lamallae, found in the compact bone of human. Down
the middle of each of these systems is a hollow tube that holds a blood
vessel. Each compact bone in the human body has many haversian
system that line up next to each other, creating a dense structure.
Drifting osteons are a phenomenon that is not fully understood. A
“drifting osteon” is classified as one that runs both longitudinally as
well as transversely through the cortex. An osteon can drift in one
directions several times, leaving a tail of lamellae behind the advancing
haverian canal.
Within the lamellae of each Haversian system are a series of spaces
called lacunae. The lacunae hold the osteocytes, or bone cells. These
osteocytes, along with the collagen and calcium phosphate that
makeup the matrix of the lamellae, ensure that compact bone is very
strong. There are also osteoblasts in the area that become osteocytes.
The blood vessel that runs down the middle of a Haversian system
provides nutrients to the living bone tissue. Nerves and lymph vessels
are also found in Haversian canals. These accessory tissues help with
immune response in the bones and also pick up signals from various
stimuli. The haversian canal was named after a British physician
CLOPTON HAVERS. Havers published and lectured about the
microscopic makeup of the canals he had seen in the bone. His theory
about the function of the canals was that they provided the oils
necessary to harden the bone around it. The exact function of
Haversian system is not known, and they are not present in many
vertebrate animals. Some theories as to their function are that they
repair damaged bone tissue, reduce stress on the compact bone, and
give muscle a place to anchor. Necrotic, or dying tissues so they can be
replaced by new osteocytes. These areas are known as resorption
spaces and require the help of blood vessels that bring nutrients to the
surrounding tissues.
HISTOLOGY OF THE MUSCLE TISSUES AND ITS
TYPES
Muscle tissue is a soft tissue that composes muscle in animal bodies,
and gives rise to muscles’ ability to contract. This is opposed to other
components or tissues in muscle such as tendons or perimysium. It is
formed during embryonic development through a process known as
MYOGENESIS. Muscle tissue varies with function and location in the
body.
In mammal, the 3 types are;
 Skeletal or striated muscle
 Smooth or non-striated muscle
 Cardiac or semi-striated muscle

Skeletal muscles
Contractions move part of the skeleton. Also called voluntary
because usually its contractions are under your control. It has a
stripy appearance, because of the repeating structure of the
muscle; there are many myofibrils (fibers), each one of which is
made up of repeating units called muscle sarcomeres. Each
sarcomeres is 2.5mm long. Connective tissue elements surround
muscle fibers. Individual muscle fibers are surrounded by a
delicate layer of reticular fibers called the endomysium. Groups of
fibers are bundled into fassicles by thicker CT layer called the
perimysium. The collection of fassicles that constitutes one
muscle is surrounded by a sheath of dense CT called the
epimysium, which continues into the tendon. Blood vessels and
nerves are found in the CT associated with muscles. The
endomysium contains only capillaries and the finest neuronal
branches.
Cardiac muscles
It makes up the muscular walls of the heart (myocardium). It is
involuntary because its contractions are not under your control.
However, it has a similar ultrastructural organization to skeletal muscle.
So, it too has a stripy appearance because of the repeating units called
muscle sacromeres. Cardiac muscle cells are joined to one another in a
linear array. The boundary between two cells abutting one another is
called an intercalated disc. Intercalated discs consist of several types of
cells junctions whose purpose is to facilitate the passage of an electrical
impulse from cell to cell and to keep the cells bound together during
constant contractile activity.
 Smooth muscles
It is found in the walls of most blood vessels and tubular organs
such as the intestine. It is also involuntary. However, it does not
have a stripy appearance, because it does not have repeating
sarcomeres. The contractile proteins, myosin and actin are much
more randomly arranged than in skeletal or cardiac muscle.
Smooth muscle fibers are generally arranged in bundles or sheets.
Each fiber is fusiform in shape with a thicker central portion and
tapered at both ends. The single nucleus is located in the central
part of the fiber. Fibers do not branch. They range enormously in
size from 20 (in wall of small blood vessels) to 500 (in wall of
uterus during pregnancy) micrometers. Smooth muscle fibres lie
over one another in a staggered fashion (tapered part of one fibre
over thicker part of another). In longitudinal sections, it is often
not possible to distinguish the fibre boundaries, and smooth
muscle may closely resemble connective tissue (bundles of
collagen). Where smooth muscle bundles are interlaced with
bundles of connective tissue (e.g in the uterus), one can
distinguish the smooth muscle by the orientation of the nuclei (all
oriented in the same direction), and the greater abundance of
nuclei per unit area (every smooth muscle cell has a nucleus,
fibroblast nuclei are more scattered in bundles of CT). Also
smooth muscle nuclei often have a corkscrew shape in
longitudinal section due to contraction of the muscle fibre during
fixation. In cross section, smooth muscle appears as profiles of
various sizes, depending on whether the cut went through the
thick central part or tapered end of any individual fibre. Nuclei are
seen only in the thicker profiles.
One distinguishing physiological feature of smooth muscle is its
ability to secrete connective tissue matrix. In the walls of
blood…….
Skeletal muscle
Smooth muscle
Cardiac muscle
Skeletal and cardiac are also called striated because they have dark and
light bands running across the muscle width when they are looked at
under the microscope.