Unit 10 Slides
In Unit 2 you studied a variety of animal tissues. The following
material is designed as a review and amplification of the material presented
previously. Here you will be concentrating on connective tissue (specifically
bone and cartilage) and muscle tissue.
||Slide 1 is of hyaline cartilage, the most common type
of cartilage. Note the clusters of large cartilage cells located in spaces
in the extracellular gel matrix. In cartilage the cells are embedded in
an amorphous matrix of ground substance reinforced by an interlacing network
of fine collagen fibers which cannot be distinguished by light microscopy.
These fibers give the matrix a rubbery consistency. Cartilage can support
great weight, yet it is often flexible and somewhat elastic. Note that
there is no well-developed blood supply in cartilage, which is why damage
to cartilage takes so long to heal.
||Slide 2 is a cross-section of compact bone. Bone is
living tissue and has a hard, relatively rigid matrix. The matrix contains
numerous collagen fibers and is impregnated with inorganic salts, primarily
calcium phosphate. Compact bone is composed of numerous structural units
called Haversian systems. Each Haversian system is seen as a nearly round
area. The circular core of each system is the Haversian canal that runs
lengthwise through the bone. Blood vessels and nerves run through the Haversian
canals. Around the Haversian canal is a series of concentrically arranged
hard lamellae, perforated by elongate dark areas, called lacunae, in which
the bone cells (osteocytes) are located. The numerous very thin dark lines
running radially from the central canal across the lamellae to the lacunae
are the canaliculi. These channels connect the bone cells to one another
and to the Haversian canal. They provide the "highways" through
which tissue fluid, oxygen, and nutrients can reach the widely separated
cells, imprisoned as they are in a desert of solid matrix.
Muscle or Contractile Tissue
||Slide 6 is a longitudinal section of striated muscle.
Notice that each cell (or fiber, as it is usually called) is roughly cylindrical,
contains many nuclei (dark spots, usually found at the edge of the fiber)
and is crossed by alternating dark and light bands called striations. The
fibers are usually bound together by connective tissue into bundles.
||Slide 7 is a cross-section of a skeletal muscle. Note
the peripheral location of the nuclei. In the unfixed tissue the fibers
are round but during fixation they become artificially polyhedral. (C =
blood capillaries; P = strand of connective tissue.)
Slide 8 is a high-power view of a single
striated muscle fiber in longitudinal view. Note the peripheral locations
of the nuclei and the definite striations.
||Slide 9 shows several neuromuscular junctions. The dark
lines entering from the center right and going to the individual muscle
fibers are motor neurons. A specialized structure, the neuromuscular junction
is formed from the end of the axon and the adjacent portion of the muscle
surface. Transmission across this gap is by transmitter chemicals. Cells
of skeletal muscle are innervated by a single nerve fiber from the somatic
||Slide 10 is a longitudinal section of smooth muscle.
Smooth muscle fibers interlace to form sheets of muscle rather than bundles.
Each fiber is elongate, pointed at each end, and contains a single, centrally
located nucleus. There are no striations. Smooth muscle fibers are innervated
by the autonomic nervous system; each fiber has both SANS and PANS innervation.
||Slide 11 is a longitudinal section of cardiac muscle.
Cardiac cells often branch and interdigitate, thus forming the complex
three-dimensional network seen here. The tiny brown cells seen in spaces
between the fibers are red blood cells; cardiac muscle is well supplied
with blood. Notice that cardiac muscle has some of the attributes of smooth
muscle, and some of striated muscle. There are striations but these are
not as apparent as in striated muscle. Like smooth muscle, each fiber has
a single nucleus. Cardiac muscle is innervated by both divisions of the
autonomic nervous system.
||Slide 12 is a longitudinal section of cardiac muscle
at a higher magnification. The muscle fibers branch and interdigitate,
but each is a complete unit surrounded by a cell membrane. The thick dark
line in the center, marking the junction between two cells, is an intercalated
disk. These are places where one cell ends and the next begins; here the
membranes of both fibers parallel each other through an extensive series
of folds. They provide a strong union between fibers, so a pull of one
contractile unit can be transmitted along its axis to the next. These are
also places where electrical stimuli can pass directly from one cell to
||Slide 13 shows bacterial flagella. Many bacteria actively
move about by means of flagella arising from one or both ends of a cell,
or from the entire surface. These flagella are quite different from the
flagella and cilia of eukaryotes. Eukaryotic flagella propel cells with
a wavelike motion, utilizing the energy of ATP. By contrast, bacterial
flagella are thin helical filaments that propel the cells with a propeller-like,
rotating motion. The energy for this process does not come from ATP directly;
a proton pump is involved. When a cell has more than one flagellum, the
flagella cluster together and rotate as a single bundle. The flagella propel
the cell by rotating in a fashion similar to the propeller of a ship.
||Slide 14 shows longitudinal and cross-sections of eukaryotic
flagella. Note the 9 + 2 arrangement of the microtubules.