CTO Quiz #4

Question 1

Which cells of the bone marrow can regenerate themselves?

Answer 1

Pleuripotent and multipotent stem cells can reproduce themselves. All other cells are committed to differentiating.

Question 2

What are the changes in cell appearance of blood cell precursors as blood cells differentiate?

Answer 2

Cells become smaller; lose nucleoli; develop granules; nucleus assumes a more adult shape.

Question 3

Which hematopoietic cells have the greatest mitotic activity?

Answer 3

Blast cells are the most mitotically active.

Question 4

What is the primary growth factor that stimulates erythropoiesis and where is it made?

Answer 4

Erythopoietin (EPO): stimulates RBC development and is made in the kidney.

Question 5

What is the most important interleukin to stimulate the production of all myeloid cells and what cells produce it?

Answer 5

IL-3 is producted by T-lymphocytes and stimulates production of all myeloid cells.

Question 6

What are the two most important growth factors that stimulate granulocyte production and what produces them?

Answer 6

G-CSF is produced by macrophages, endothelum and fibroblasts and stimulates granulocyte development. GM-CSF is produced by lymphocytes, endothelium and fibroblasts and stimulates both granulocyte and macrophage development.

Question 7

What is the most important growth factor stimlating production of platelets and where it it made?

Answer 7

Thrombopoietin is produced by the liver and kidney and stimulates the production of platelets.

Question 8

What is the first site of RBC production? What are the second and third sites?

Answer 8

The yolk sac is the first site, with the liver and spleen following.

Question 9

When does the bone marrow start producing RBCs?

Answer 9

About the middle of fetal life is when the bone marrow start producing RBCs.

Question 10

In a normal, term infant, what site(s) is/are active in producing RBCs?

Answer 10

Only the bone marrow is producing erythrocytes by the time of birth.

Question 11

In the adult, where would you expect to find red marrow?

Answer 11

Red marrow would be found in in vertebra, pelvis, ribs and sternum. Yellow marrow would fill the marrow cavity of long bones.

Question 12

What kind of cells would you expect to find in the extravascular compartment of the bone marrow? What kind of fibers?

Answer 12

Bone marrow contains hematopoietic cells, adventitial cells (stromal cells) and fat cells. The great majority of fibers are reticular fibers.

Question 13

What is meant by a “hypercellular marrow”?

Answer 13

A marrow that has too many hematopoietic cells and not as much fat as normal. It is an indicator of increased blood cell production (either physiologically because of demand or pathologically because a cell is overproducing).

Question 14

What is the structure of the vascular compartment of the bone marrow?

Answer 14

There are venous sinusoids with a discontinuous and fenestrated endothelium.

Question 15

What is an erythoblastic island and what is at its center?

Answer 15

An erythroblastic island is a cluster of developing RBCs around a macrophage (which appears to recycle iron)

Question 16

How long does erythopoiesis take?

Answer 16

Erythropoiesis takes about a week.

Question 17

What are the stages of erythropoiesis from the earliest recognizible stage?

Answer 17

Proerythroblast; basophilic erythroblast; polychromatophilic erythroblast; orthchromatophilic erythroblast; reticulocyte; erythrocyte.

Question 18

At what stage does the erythrocyte lose its nucleus, and what happens to it?

Answer 18

Between the orthochromatophilic erythroblast and reticulocyte it is extruded and phagocytosed by the macrophage.

Question 19

How long does it take a reticulocyte to mature to an RBC? How long do reticulocytes last in the bloodstream? About what percent of RBCs are reticulocytes?

Answer 19

It takes about 2-3 days for a reticulocyte to mature to an RBC and it circulates for about a day before it is a completely mature RBC. There are about 1% reticulocytes in the blood because RBCs last for about 120 days in the circulation.

Question 20

How long does granulopoiesis take?

Answer 20

Granulopoiesis takes about two weeks. During the first week there is rapid reporduction of cells and the second week is dominated by maturation.

Question 21

What are the stages of production of a neutrophil?

Answer 21

Myeloblast; promyelocyte; myelocyte; metamyelocyte; band cell; and mature neutrophil (PMN).

Question 22

What does an increase in band cells indicate?

Answer 22

It indicates the release of immature PMNs from the bone marrow, often due to increased demand due to infection.

Question 23

What does the megakaryocyte nucleus look like?

Answer 23

The megakaryocyte nucleus is multi-lobed due to endomitosis.

Question 24

What is unusual about structure of the megakayocyte (outside of the nucleus)?

Answer 24

It has a large amount of actin and mictotubules associated with long protoplasmic extensions (that enter the vascular space). There are many infoldings of the plasma membrane that are called “demarcation membranes” that provides extra membrane to allow etension of the processes of these cells.

Question 25

What is the approximate ratio between myeloid and erythroid precursors in the marrow?

Answer 25

The myeloid:erythroid ration is about 3:1 in normal marrow.

Question 26

What kind of epithelium lines the nasal cavity, trachea and main stem bronchi?

Answer 26

Pseudostratified columnar epithelium w/cilia and goblet cells.

Question 27

What are the functions of the nasal mucosa?

Answer 27

It warms and moistens air and traps particles in the air. It also contains olfactory epithelium.

Question 28

What is the direction of movement of cilia in the nasal cavity and the trachea?

Answer 28

The cilia move mucous and particles toward the oropharynx.

Question 29

What is the epithelium over the vocal cords?

Answer 29

The vocal cords have non-keratinized stratified squamous epithelium

Question 30

What is the structure of the trachea?

Answer 30

The trachea has a typical respiratory epithelium. There is a prominent lamina propira with serous and mucous glands. The submucosa contains hyaline cartilage in a “C” shape which is open posteriorly. There is smooth muscle that is particularly prominent posteriory, where there is also a lot of fibroelastic tissue. The entire organ is surrounded by an adventitia. There is lymphoid tissue that is particularly prominent in the lamina propria (MALT).

Question 31

What are the differences between the trachea and bronchi?

Answer 31

Bronchi have cartilage plates instead of incomplete rings and there is more smooth muscle.

Question 32

What is the only complete cartilage ring in the respiratory system?

Answer 32

The cricoid cartilage at the lowest part of the larynx.

Question 33

What cell types can be found in the epithelium of the bronchi?

Answer 33

Columnar cells with cilia (mucociliary escalator); goblet cells; brush cells (sensory function); neuroendocrine K cells; basal cells (stem cell capabilites).

Question 34

What are the structural differences between bronchi and bronchioles (other than size)?

Answer 34

There are more smooth muscle cells and elastic fibers in bronchioles. The cartilage and the glands of the lamina propria are gone. The respriatory epithelium of the bronchioles becomes ciliated simple columnar or cuboidal in shape and clara cells replace goblet cells. These cells secrete protein/glycoprotein/surfactant material to keep the bronchioles from collapsing.

Question 35

What is the difference between respiratory bronchioles and the remainder of the bronchioles?

Answer 35

The wall of the respriatory bronchioles has some areas of simple columnar/cuboidal epithelium and some areas directly opening into alveoli.

Question 36

What are alveolar ducts?

Answer 36

Alveolar ducts are air passages that are lined entirely by alveoli.

Question 37

What are alveolar sacs?

Answer 37

Alveolar sacs are dead-end clusters of alveoli.

Question 38

What is the structure of the alveolar wall?

Answer 38

Alveoli are lined by simple squamous epithelium (type I pneumocytes) which comprise 95% of the area of the alveolar surface. There are type II penumocytes that are thicker and that contain lamellar bodies, which can be secreted as surfactant. Type II pneumocytes are more common and can reproduce to replace the type I pneumocytes.

Question 39

What are the pores of Kohn and what do they do?

Answer 39

The alveoler pores of Kohn equalize pressure between alveoli.

Question 40

What is the function of alveolar “dust cells”?

Answer 40

These are macrophages that phagocytose particulate matter that might be inhaled.

Question 41

What is the minimum membrane for gas exchange?

Answer 41

The minimum membrane for gas exchange is the type I pneumocyte, the common basement membrane and the alveolar capillary endothelial cell.

Question 42

How do the blood vessels distribute to the alveoli?

Answer 42

The arteries travel with bronchi and bronchioles (get oxygenated by alveoli), while the veins travel in the elastic connective tissue septa between lung segments.

Question 43

What do nerves do in the lung?

Answer 43

Parasympathetic nerve fibers (from the vagus) constrict bronchial smooth muscle and increase glandular secretion. Sympathetics relax bronchial smooth muscle and decrease secretion. Sensory fibers mostly detect stretch of the elastic connective tissue (Hering-Breuer afferents). These are pulmonary stretch detectors. There are also afferent nerve fibers to the mucosa that participate in cough (particularly in the trachea and carina region).

Question 44

What are the functions of the integument (skin)?

Answer 44

It is the largest organ in the body. The functions include: protection; temperature regulation; production of Vitamin D (via photochemical reaction); excretion of wastes through sweat glands; sensation

Question 45

What are the layers of the integument?

Answer 45

The epidermis, the dermis and the hypodermis (superficial fascia).

Question 46

What are the layers of the epidermis?

Answer 46

It is a stratified squamous kenatinized epithelium comprised of layers of keratinocytes (make keratin). The layers of epidermis include (from deep to superficial): the statum basale; the stratum spinosum; the stratum granulosum; and the stratum corneum.

Question 47

How long does it take to replace your epidermis?

Answer 47

Your entire skin is replaced approximately evey month.

Question 48

What is the stratum basale?

Answer 48

The stratum basale is the deepest layer of the epidermis. It is one cell layer thick with all cells touching the basal lamina and attached to it by hemidesmosomes. These cells are cuboidal in shape and are mitotic. They form stem cells for generation and replacement of the keratinocytes. These cells have basophilic cytoplasm because of lots of ribosomes synthesizing keratin. These cells also contain pigment granules (melanosomes) that are produced by melanocytes, but phagocytosed by keratinocytes.

Question 49

What is the stratum spinosum?

Answer 49

This is the thickest layer. It is comprised keratinocytes that have been generated by the basal cells and that lose attachment to basement membrane. These cells are connected to one another by desmosomes that give the cells the appearance of spines when they shrink away from one-another. The intermediate filament (keratin) groups into tonofibrils that attach to desmosomes and hold cells together.

Question 50

What is the stratum granulosum?

Answer 50

The cells of the stratum granulosum layer contain basophilic granules of keratohyalin (clumps of protiens including filaggrin) that hold tonofibrils together. The cells assume a more flattened shape but still have a nucleus. They also accumulate lamellar bodies (granules), which spill out of the cell to produce a barrier to water movement through the skin (out or in). In thick skin, there is a very thin, highly eosinophilic layer at the superficial transition area called the stratum lucidum.

Question 51

What is the stratum corneum?

Answer 51

The stratum corneum consists of dead cells filled with keratin and no nuclei. There are still desmosomes (hold cells of the deeper layers together) while superficial are sloughed off. There is lipid (from the lamellar bodies) between cells.

Question 52

What other kinds of cells are present in skin?

Answer 52

The skin also contains melanocytes (pigment), Langerhans cells (phagocytic and antigen-presenting), and Merkel’s cells (sensory function).

Question 53

What are melanocytes?

Answer 53

These are cells that derive from from neural crest cells. They have processes that contact up to 30 keratinocytes. They manufacture eumelanin and pheomelanin that are not colored (despite the fact that they will make brown and red pigment, respectively). The processes of the melanocytes are phagocytosed by keratinocytes that metabolize the product into a pigmented product. The color of skin does not depend on the number of melanocytes but rather the rate and of transfer to the keratinocytes and density within the keratinocytes.

Question 54

What are Langerhans cells?

Answer 54

These are phagocytic and anitgen processing cells (they present anitigen to T-Lympocytes). They are pale staining with many processes, called dendrites (despite the fact that these are not neural). They are mostly found in stratum spinosum and are responsible for skin immune reactions, including allergic reactions.

Question 55

What are the layers of the dermis?

Answer 55

The more superficial layer of the dermis is the papillary layer. It is loose connective tissue with many blood vessels. It makes papillae (rete pegs) that stick up into the epidermis and increase contact area. The papillae are responsible for fingerprints. This layer contains nerves, fibroblasts and macrophages. The deeper layer is the reticular layer. This is comprised of dense irregular CT with more collagen & elastin fibers than papillary layer. The sweat glands stick down and through this layer.

Question 56

What is the structure of the hypodermis?

Answer 56

This is made of loose CT with fat, nerves and sweat glands. It acts as a shock absorber and allows skin to slide over underlying structures. It is also known as the superficial fascia.

Question 57

What is the structure of a hair follicle?

Answer 57

A hair follicle is composed of a root sheath with a bulb at the bottom of the tube. There is a dermal papilla that enters the bulb and nourishes it. The hair matrix (the growing part) surrounds the papilla and melanocytes provides hair color. The hair shaft is made of medulla (inner layer), cortex (middle layer) and cuticle (outer layer, highly keratinzed and roof shingle appearance). There are sebaceous (oil) glands that empty into the follicle and arrector pilli muscles (smooth, involuntary) contract to lift hair up and cause goosebumps.

Question 58

What kind of glands are sebaceous glands?

Answer 58

These are holocrine glands and secrete an oily secretion.

Question 59

What is the structure of eccrine sweat glands and where are they found?

Answer 59

These are simple coiled tubular glands found in the deep dermis and hypodermis. They empty by coiled tubular glands and secrete via merocrine secretion. In addition to their function in evaporative cooling, they secrete salt, urea and lactate. There are myoepithelial cells to help expel secretions.

Question 60

What are “azurophilic granules”?

Answer 60

Azurophilic granules are lysosomes that are present in all granulocytes. They can also be seen in monocytes.

Question 61

What are apocrine sweat glands and where are they found?

Answer 61

These are simple coiled tubular glands found in the axilla and anogenital region. The lumen is large because secretions are stored in the lumen. They use merocrine sectetion and, although the secretions themselves are generally odorless, bacterial action causes the odor.

Question 62

What is the structure of the mammary glands?

Answer 62

These are compound tubuloacinar glands that develop along the “milk line”. The use apocrine (lipids) and merocrine (antibodies, proteins and sugars). Under the influence of hormones (including prolactin) the ductal system becomes more complex and develops secretory aveoli (simple cuboidal or columnar epithelium with myoepithelium). Milk is released into lactiferous ducts (simple cuboidal) then lactiferous sinuses. Oxitocin stimulates the myoepithelium to eject milk (“letdown”).