Limbs Histology Labs

Front 1

Back 1

Non-descript
morphology. Can sometimes see extracellular stuff excreted (indicating fibroblasts)

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Back 2

Embryonic connective tissue. Non-descript morphology, looks like a bunch of loose fibroblasts.

Front 3

Back 3

Fibroblasts that are starting to secrete extra cellular material. Remember this material is divided into fibrous and amorphous.

Front 4

Back 4

Remember there are no loose and regular collagen bundles only loose and irregular

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Back 5

Connective tissue at low resolution. Although labeled, Djakiew does not expect us to know these cells at
this level of resolution. However, since the same pictures show up on the exams it may be helpful to
memorize the labeled ones on the slide (probably not)

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Back 6

Plasma cell at high res. Eccentric nucleus. Cartwheel arrangement of heterochromatin.

Front 7

Back 7

EM of plasma cell. Easier to see the cartwheel arrangement. Can see cytoplasm filled with RER (making lots of antibodies = proteins).

Front 8

Back 8

Macrophages at high res. They float around in connective tissue, phagocytose things, and are derived
from monocytes. Tough to recognize in normal connective tissue until we inject with Indian ink seen in
slide 10.

Front 9

Back 9

Indian ink was injected and phagocytosed by the macrophages = functional test. Notice all the blackness
surrounding a red center (those are you macrophages!)

Front 10

Back 10

Adipose Cells. Unilocular cell because lipid droplet fills the entire cell.

Front 11

Back 11

Slightly lower magnification of more unilocular adipose cells. Stained with oil Red O. Notice the blood vessels going around the adipocytes.

Front 12

Back 12

EM of fat cells. Cells are black around the outside due to oxidation of fat with the osmium tetroxide
treatment. The cells in the middle are not stained because the lipid was dissolved away.

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Back 13

Mast cell. Contains lots of granules (heparin = anticoagulant, histamine = vasodilator, increase cellular
permeability). You can see some granules being released into the surrounding connective tissue along
the right side.

Front 14

Back 14

EM of mast cell. Large secretory granules are evident. Along the right side labeled as “2” are Type I
collagen fibers.

Front 15

Back 15

Leukocytes. Who knew we had blood in connective tissue? In case you forgot your MCP, look @ next slide....

Hint 15

Front 16

Back 16

From outside to inside: Dense squamous integument! epidermis (reddish) ! dermis (salmon pink
color). Dermis = dense and irregular connective tissue because the fibroblasts and collagen are packed pretty tightly and the orientation is irregular (not uniformly laid down). Dermis is useful for making shoes because it’s so dense ! LEATHER!

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Back 17

Lamina propria = generic term for loose connective tissue that underlies a lot of glands and organs. This particular picture is of the GI tract. Notice the large venule and be able to recognize the plasma cells
(eccentric nuclei) and lymphocytes (no cytoplasm).

Front 18

Back 18

Dark staining material is cellular component of fibroblast. Lighter staining material are the collagen
fibers secreted by fibroblasts to make up the extracellular matrix. Recognize the difference between the longitudinal sections and cross sections.

Front 19

Back 19

Appreciate this picture for being able to see the collagen fibers running in all different directions which makes it irregular connective tissue. Close packing makes this dense connective tissue.

Front 20

Back 20

Tendon = dense regular connective tissue. You can kind of see a line of nuclei of fibroblasts in the
middle but most of this picture is extracellular dense regular connective tissue.

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Back 21

Dense regular connective tissue with elastin fibers. Although wavy, everything is running in the same direction so this connective tissue is considered regular

Front 22

Back 22

Reticular fibers = special example of collagen (Type III) that stains black with silver based stains. Concentrated in lymph node organs such as spleen, thymus, etc.

Front 23

Back 23

Hyaline cartilage = amorphous connective tissue. You know this is hyaline cartilage because there are
no elastin fibers and you can see the characteristic perichondrium on the right. The perichondrium
differentiates to the chrondroblasts and then the chrondrocytes as you move toward the left.
Chondroblasts will have no ring while chondrocytes with have a light staining territorial matrix around
it.

Front 24

Back 24

Another picture of hyaline cartilage with the perichondrium on top. The territorial matrix is especially clear here, therefore, the circled area contains chondrocytes. Remember that the term for the growth of hyaline cartilage is appositional.

Front 25

Back 25

All articular cartilage are examples of hyaline cartilage. We know that we have articular cartilage here
because of its articulating location. There is NO PERICHONDRIUM since all articular cartilage is
derived from interstitial growth.

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Back 26

You can see interstitial growth here by mitosis. You can get interstitial growth in regular hyaline cartilage in addition to growth from the perichondrium.

Front 27

Back 27

Elastic cartilage with the perichondrium barely seen on the right side. Elastic fibers are obvious
throughout this preparation. NO INTERSTITIAL GROWTH in elastic cartilage. All growth is derived
from the perichondrium.

Front 28

Back 28

Fibrocartilage which is contained in high stress areas such as the intervertebral disc or pubic symphysis.
NO PERICHONDRIUM which means it grows by interstitial mitosis only. You know its fibro cartilage
because of the long linear array of cells.

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Back 29

Epiphyseal Growth plate. Chrondrocytes between the dark lines are growing interstitially by mitosis (NO PERICHONDRIUM). These are replaced on the trailing edge by newly formed bone.

Front 30

Back 30

Chondroblasts on EM because NO territorial matrix observable. If you want you can look at the
interterritorial matrix which is made of amorphous material masking type II collagen.

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Back 31

This looks like the chondroblast EM but has a light staining ring around the cell (territorial matrix)
which means we have chondrocytes.

Front 32

What is this?

Back 32

???

Front 33

Back 33

Skeletal Muscle – Longitudinal Section
Note that the nucleuses of skeletal muscle cells
are found in the periphery (I circled them in the picture to the right, the nuclei don’t particularly stand out and are pretty flat and narrow)

Front 34

Back 34

Skeletal Muscle – Cross Section
Similarly, note that nuclei are in the periphery of skeletal muscle cells (denoted as “N”) in the slide.
BV are blood vessels, and little “stars/asterisks” on the slide on the right are capillaries 7-9um across
which is just enough for a red blood cell to go through.

Hint 34

note nuceli on outside

think where & what layer of connective tissue surrounds it

Front 35

Back 35

Sacromere (longitudinal)
This slide shows the banding patterns, and shows the different regions for you. I’d know this well since it is very testable. Sarcomere is the functional unit of a muscle and is from Z-line to Z-line. A-band does NOT change in length during muscle contraction. This is a relaxed muscle since I-band is pretty
wide.

Front 36

*is this a relaxed or contracted muscle?

Back 36

I band present= relaxed
Skeletal Muscle Sarcomere (longitudinal)
Relaxed muscle due to presence of wide I-band. The mitochondria on this slide are pretty clear (denoted “M”). Try to locate a sarcomere (hint: Z-line to Z-line) and a H-band by yourself.
Td denotes Triad, containing T-tubule (denoted “T”, an extension of the sarcolemma), Tc denotes terminal cisternae which are parts of sarcoplasmic reticulum. There are 2 Tc’s and one T in a triad.

Hint 36

t-tubules from scarcolemma

Front 37

Back 37

Skeletal Muscle Sarcomere (longitudinal)
Note the A-band, Z-line, H-band and Triad. Dr. Andrew’s said that this sarcomere section was not from a human since in humans it should be in the A-I junction and should never cross the Z-line.

Hint 37

ID: T-Tuble? sarcoplasm reticulum? A band? H band? (any actin found in H band? NO!!)

Front 38

ID: Z-line, I band, A-band H-band, Triad, mitochondria

Back 38

“We are going to reiterate this since this might be on the exam” is what Dr. Andrew’s said verbatim.
Identify the Z-line, I-band, A-band, H-band. It is a triad in a circle. Mitochondria is the dark mass in the top right.

Front 39

Back 39

“We are going to reiterate this since this might be on the exam” is what Dr. Andrew’s said verbatim.
Identify the Z-line, I-band, A-band, H-band. It is a triad in a circle. Mitochondria is the dark mass in
the top right.

Hint 39

Unless you see one fiber next to one another, there is no way to know which band is thicker

Front 40

*WILL BE ON EXAM!! are we looking at H-band, I band, M Line?

Back 40

I Band
Small filaments=actin
large=myelin

“We are going to reiterate this since this might be on the exam” is what Dr. Andrew’s said verbatim.
Identify the Z-line, I-band, A-band, H-band. It is a triad in a circle. Mitochondria is the dark mass in
the top right.

Hint 40

Front 41

Back 41

“We are going to reiterate this since this might be on the exam” is what Dr. Andrew’s said verbatim. Identify the Z-line, I-band, A-band, H-band. It is a triad in a circle. Mitochondria is the dark mass in the top right.

Hint 41

Front 42

Back 42

EM Cross-section of A band
You get thicker myosin and thinner actin in a A-band cross-section, restating the obvious.

Hint 42

Front 43

Back 43

MOTOR UNIT
Know what the motor end-plates look like.

Front 44

*Ppoint out Ach vesicles, junctional clefts, junctional fold

Back 44

MOTOR END PLATE
jxnl folds increase surface area

Hint 44

Front 45

Back 45

Muscle Spindle (INTRAFUSAL FIBERS)(scanning power view)
Spindle shaped unit surrounded by connective tissue, called muscle spindle. Fibers inside the “circle”
with a large yellow pointing to it are known as intrafusal fibers, and fibers outside are called extrafusal
fibers. This slide should be taken from embryonic material, as extrafusal fibers should be much larger than intrafusal fibers. These extrafusal fibers have not hypertrophied yet.

Hint 45

Front 46

Back 46

MUSCLE SPINDLE

Notice the difference in diameters between the intrafusal skeletal muscle fibers (I.e. those within the muscle spindle) compared to the much larger extrafusal fibers.
Note blood veseels as well (contain RBC, duh!) No RBC present, == LYMPHATIC TISSUE

Hint 46

Muscle Spindle
Adult, note the larger extrafusal fibers, and the more or less spindle shaped intrafusal fiber surrounded by connective tissue. The blood vessels are red in color in the slide and are pretty obvious.

Another demonstration of the organization of extrafusal and intrafusal fibers in muscle spindles. Muscle spindles serve the functions of strain gauges and proprioception.

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Back 47

Low power, cant see much... Skipped

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Back 48

Cardiac Muscle
Note that the nuclei are at the center of the cells. Identify the intercalated disks (marked by a yellow arrow pointing up). They are made up of GAP JUNCTIONS (electrically coupled), fascia adherens and DESMOSOMES. Please refer to his handouts for lecture #13 for more details. Also note the BRANCHING OF CARDIAC MUSCLE CELLS. (Note: mitochondria are absent in this slide since they are not specifically stained)

Hint 48

white gaps= cappilaries

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Back 49

EM: Cardiac Muscle
Lots 'o mitochondria.
D= intercalated disks.
F= fibroblast.

Front 50

Back 50

EM: Cardiac Muscle
Notice ***** ASS MOTHAFUCN MITOCHONDRIA ALL OVER THE PLACE in cardiac muscle cells

Front 51

Back 51

EM: Intercalated Disk
Identify the A-band, I-band, Z-line, mitochondria.
FA= FASCIA ADHERENS
N= Nexus / Gap Junctions.
Super thin structure between cells
G= glycogen

Front 52

Back 52

Lipids are the same circular shaped, the other electron-dense structures are mainly mitochondria.

Hint 52

notice lipid, fat, mitochondira

Front 53

Back 53

PURKINJE FIBERS!!
ID fibers, endocardium
White= chamber inside heart

Hint 53

Front 54

Back 54

Atrial Natriuretic Granules, more for physiology, not going into that.

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Back 55

Smooth Muscle
Illustration of how smooth muscle looks like in its CONTRACTED STATE.

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Back 56

Urinary bladder smooth muscle
Smooth muscle in the urinary bladder is necessary for its contractile function.

Front 57

Back 57

Small Intestine
Very low magnification section through the small intestine, TWO LAYERS of smooth muscles to produce the PERISTALTIC WAVES in the intestines.

Front 58

Back 58

. Smooth Muscle – Longitudinal & X-section
Note the inner circular layer and outer longitudinal layer of smooth muscle. Probably in the (small) intestines.

Front 59

Back 59

Vascular Smooth Muscle
Notice the “cork screw” appearance of the smooth muscle nuclei. This is seen if the muscle cells are fixed in a contracted state. It will not be seen if the cells are elongated or stretched.

Hint 59

Vascular Smooth Muscles
Muscular arteries have a lot of smooth muscles, note the lumen, internal elastic lamina, external elastic lamina (don’t worry about IEL and EEL yet. More coming up in CP). The convoluted appearance of smooth muscle suggests that the artery is constricted. The nucleus of smooth muscles exhibit a cork-screw appearance during smooth muscle contraction.

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Back 60

EM: Smooth Muscle
N = nuclei. That’s all he covered in this slide.

Front 61

*This picture appeared multiple times

Back 61

Smooth Muscle Caveolae
Note the conical arrangement of organelles on either poles of the nucleus. Be able to identify the nucleus (right edge, in the center), ER, mitochondria (M). (note: this slide is also slide #45 from lecture 13, in case you were wondering.)

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Back 62

Cross-section through an arteriole in contracted state

Front 63

Back 63

Centrally located nucleus. Most organelles (dark staining = mitochondria) are arranged on either poles
of the nucleus.

Hint 63

Centrally located nucleus. Most organelles (dark staining = mitochondria) are arranged on either poles of the nucleus.

Front 64

Back 64

Hint 64

Longitudinal section through long bone. Here we are pointed to toward the diaphysis and the metaphysis
(funnel end of the diaphysis that transitions into the epiphysis). We can also clearly see the epiphyseal
plate as well as the epiphysis and the articular cartilage. Recognize the secondary and primary
ossification centers which are the epiphysis and diaphysis areas respectively.

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Back 65

Hint 65

Epiphyseal growth plate probably taken from embryological tissue. On the left we have the resting zone
(R) which is toward the secondary ossification center. The proliferation zone (P), maturation zone (M),
hypertrophy zone (H), degeneration zone (D) and ossification zone (O) were also pointed out. The
proliferation zone cells are the ones responsive to growth hormone and thicken the plate. The right slide
is from embryological development where you can see the beginning of ossification at the diaphysis
(bottom) but don’t yet see the secondary ossification center at the top since it is still all cartilage.

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Back 66

Hint 66

Pink stain shows the diffusion of calcium salts (pink) into the cartilage plate (blue). The key things to notice about this slide and the next slide is the edge of growth plate being slowly ossified and the demarcation of the calcium salts and cartilage.

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Back 67

Hint 67

Another example of the mechanistic ossification of the growth plate. Calcium phosphate is stained black
and can be seen penetrating into the trailing edge of the growth plate.

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Hint 68

Periosteum as the dense cellular area on the right. Adjacent to the periosteum (reproduced to the right) we see we see these plump periosteum fibroblasts that are not yet attached to bone.
These are BONE BLASTEMAS. To the left of this is spongy bone. On the inner surface to the left
of the spongy bone would be the endosteum.

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Back 69

INTRAMEMBRANEOUS OSSIFICATION

Hint 69

Another view of spongy bone with a focus on the periosteum. The periosteum is once again
the densely packed area (near the top). Djakiew points out some fibroblasts in the white area. In the pink
area, it is hard to make out the osteoblasts but you can see some of the osteocytes inside the gaps in the
pink spongy matter. He stressed that this periosteal area represents INTRAMEMBRANEOUS OSSIFICATION

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Back 70

Hint 70

Higher magnification so that you can now see the osteoblasts (plump dark cells lying around the pale mesenchymal tissue). The pale lining on the opposite side of the mesenchymal tissue represents the
osteoids, inorganic material that later becomes mineralized. As you can see in the dark boney area, some “osteoblasts” become trapped in their own material because of this process. We now call these osteocytes.

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Hint 71

Nicely labeled high magnification slide that shows another representation of the developing spongy
bone. Remember the osteoid is the pale area. The more pinkish area in between is the mineralized
matrix.

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Back 72

Hint 72

Similar as slide 9 but with a different stain. Osteoblasts are shown in pink and we can see the dark
plump osteocytes trapped in the mineralized matrix.

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Back 73

Hint 73

Once again, slide of periosteum (dense cell layer on top) forming spongy bone. We can see some blood vessels on this slide. If the mineralized matrix pinches off a
blood vessel, we can form a small round osteons as shown on the right which later
forms the Haversian systems.

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Back 74

Hint 74

Osteoclasts are shown as the pink bodies with multiple dark nuclei. The multinucleation is characteristic of osteoclasts since they are derived from monocytes by fusion. Osteoclasts can float around on their
own as they do here and do not need to be on bone.

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Back 75

Hint 75

More osteoclasts. The multinucleated nature is super obvious on this slide. The indentations, called
HOWSHIP'S LACUNAE , are on the top of these osteoclasts and represent where bone is being chewed away.
The ruffled border near this indentation is to increase surface area of the cell and therefore increase
reabsorption.

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Hint 76

Compact bone. We can see the osteons that have the trapped blood vessels (now Haversian canals). The arrow points to a Volkmann’s canal which bridges these the Haversian canals.

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Back 77

Hint 77

High magnification of osteons. We see two full osteons and another haversian canal to the bottom right. In addition the the lamellae surrounding these canals that make up the osteon, we can see some
interstitial lamellae which are the remnants of previous osteons that have been partially reabsorbed.
Demonstrates the constant remodeling process of bone.

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Back 78

Hint 78

High magnification of compact bone. Here we can see the osteocytes (dark areas) which send out filopodia that are communicating with adjacent filopodia via gap junctions. These filopodia are
contained within canaliculi and can form chains up of up to 20 osteocytes to transfer metabolites and
waste products through the bone in both directions.

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Back 79

Hint 79

Here we see a nice picture of the fatty marrow on the left. “a” represents the inner circumferential lamellae. To the right is an osteon with an obvious Haversian canal.

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Back 80

Hint 80

Nicely labeled and read right off the slide. This slide gives a good overall view of all the parts of the bone we’ve been discussing. Not the dark staining osteoblasts lining the endosteum.

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Hint 81

Odontoclast = osteoclast in teeth. We know it’s an osteoclast because it is multinucleated. He didn’t really specify how you would know it’s an osteoclast vs odontoclast but the slide mentions recognizing
the dentin fibers (“2” represents the tooth). I say memorizing the picture as an odontoclast one sounds
good.

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Back 82

Hint 82

SEM of piece of bone. The big gaping hole is the lacunae that had housed an osteocyte. The little holes you see are the canaliculi where the filopodia would reside in.

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Back 83

Hint 83

Lower power SEM of bone. More mature bone is smoother while the bone undergoing resorption is
rougher in appearance.

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Back 84

Hint 84

Synovial joint of finger. You can see the lighter stained articular cartilage (c) at the articulating surface.
We were pointed toward the synovial membrane between the cartilage.

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Back 85

Hint 85

Higher powered view of synovial membrane. At the surface we see the phagocytic A cells. Underneath the A cells are the secretory B cells that are secreting material into the joint cavity.

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The answer is c) Terminally differentiated since the circled area represents an osteocyte