Review Questions Flashcards
What are the layers of the epidermis?
It is a stratified squamous kenatinized epithelium comprised of layers of keratinocytes (make keratin).
The layers of epidermis include (from deep to superficial): the stratum basale; the stratum spinosum; the stratum granulosum; and the stratum corneum.
How long does it take to replace your epidermis? Where are new cells formed?
Your entire skin is replaced approximately evey month.
In the basal part of the epithelium
What is the stratum basale? What shape are the cells?
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.
Name functions of stratum basale cells?
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.
What are the functions of the melanosomes?
To protect the nuclei of the stem cells from UV damage
What is the stratum spinosum?
This is the thickest layer. It is comprised keratinocytes that have been generated by the basal cells and that lose attachment to basement membrane.
What connects cells in the stratum spinosum?
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.
What is the stratum granulosum?
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. In thick skin, there is a very thin, highly eosinophilic layer at the superficial transition area called the stratum lucidum.
What is the function of lamellar bodies in the stratum granulosum?
They produce a barrier to water movement through the skin (out or in).
What is the stratum corneum?
Most superficial layer; consists of dead cells filled with keratin and no nuclei.
There are still desmosomes (hold cells of the deeper layers together) while superficial do not have desmosomes. There is lipids (from the lamellar bodies) between cells that form a water barrier
What is the additional layer in thick skin?
Stratum lucidum
It is between the granular and cornified layer. Has flattened cells with no organelles
Where do melanocytes come from? What colors do eumelanin and pheomelanin make? Where do melanocytes produce melanin?
These are cells that derive from from neural crest cells. They have processes that contact up to 30 keratinocytes. The processes of the melanocytes are phagocytosed by keratinocytes that metabolize the product into a pigmented product.
Eumelanin: color of black or brown hair
Pheomelanin: red hair
Produce melanin in the melanosomes.
What is the function of melanin? Why are there differences in skin color? How?
Melanin protects cells (DNA) from UV radiation; 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.
What layer are melanocytes found?
BASAL LAYER
What are Langerhans cells?
These are phagocytic and antigen processing cells (they present antigen 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 (found in all layers)
What are the functions of the Langerhans?
Responsible for skin immune reactions, including allergic reactions.
What are Merkel’s cells?
Modified keratinocytes that are in the BASAL LAYER;
Function as sensory receptors for fine touch and discrimination of form and texture
Describe papillary layer of the dermis
Has loose CT with a lot of blood vessels
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.
Describe reticular layer of the dermis
Has dense irregular CT with more collagen & elastin fibers than papillary layer.
The sweat glands stick down and through this layer.
Structure of the hypodermis?
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
Describe structure of a hair follicle
Has a root sheath with a bulb at the bottom of the tube.
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).
How is the hair follicle nourished?
There is a dermal papilla that enters the bulb and nourishes it (made from part of the dermis)
What are the functions of the sebaceous (oil) glands in hair follicles?
The sebaceous (oil) glands that empty into the follicle. Lubricate hair and skin
What kind of glands are sebaceous glands?
Holocrine glands and secrete an oily secretion.
What are the functions of the arrector pilli muscles?
arrector pilli muscles (smooth, involuntary) contract to lift hair up and cause goosebumps.
What is the structure of eccrine sweat glands and where are they found?
These are simple coiled tubular glands found in the deep dermis and hypodermis. They empty by coiled tubular glands and secrete via MEROCRINE secretion.
What is the function of eccrine sweat glands?
In addition to their function in evaporative cooling, they secrete salt, urea and lactate. There are myoepithelial cells to help expel secretions.
What are apocrine sweat glands and where are they found?
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.
What are “azurophilic granules”?
Azurophilic granules are lysosomes that are present in all granulocytes. They can also be seen in monocytes.
What is the structure of the mammary glands?
These are compound tubuloacinar glands that develop along the “milk line”. The use apocrine (lipids) and merocrine (antibodies, proteins and sugars).
What happens to mammary glands when hormones kick in?
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”).
What are keratinocytes?
Keratinocytes are the dominent cells of the epidermis (they make keratin).
What kind of epithelium lines the nasal cavity, trachea and main stem bronchi?
Pseudostratified columnar epithelium w/cilia and goblet cells.
What is the function of the olfactory epithelium?
Provides a sense of smell
What are the functions of the nasal mucosa?
It warms and moistens air and traps particles in the air. It also contains olfactory epithelium.
What is the direction of movement of cilia in the nasal cavity and the trachea?
The cilia move mucous and particles toward the oropharynx.
What is the epithelium over the vocal cords?
The vocal cords have non-keratinized stratified squamous epithelium
What is the structure of trachea? What kind of cartilage does it have and in what shape?
The trachea has a typical respiratory epithelium. 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 (helps with dilation and narrowing of trachea.
The entire organ is surrounded by an adventitia.
What is the lamina propria? What kind of tissue is in the lamina propria?
It is submucosal connective tissue that has a rich blood supply! There is lymphoid tissue that is particularly prominent in the lamina propria (MALT).
What is the function of the seromucous glands in the submucosa of the trachea and bronchi?
They drain through ducts into the lumen.
What are the differences between the trachea and bronchi?
Bronchi have cartilage plates instead of incomplete rings and there is more smooth muscle.
What is the only complete cartilage ring in the respiratory system?
The cricoid cartilage at the lowest part of the larynx.
What cell types can be found in the epithelium of the bronchi?
Columnar cells with cilia (mucociliary escalator);
goblet cells: single cell mucous glands;
brush cells (sensory function);
neuroendocrine K cells;
basal cells (regenerative stem cell capabilites).
What are the structural differences between bronchi and bronchioles (other than size)?
There are more smooth muscle cells and elastic fibers in bronchioles.
THERE ARE NO cartilage and the glands of the lamina propria are gone in the bronchioles. The respriatory epithelium of the bronchioles becomes ciliated simple columnar or cuboidal in shape and clara cells replace goblet cells.
What are the function of clara cells in bronchioles?
These cells secrete protein/glycoprotein/surfactant material to keep the bronchioles from collapsing. Also protect against toxins and carcinogens
What is the difference between respiratory bronchioles and the remainder of the bronchioles?
The wall of the respriatory bronchioles has some areas of simple columnar/cuboidal epithelium and some areas directly opening into alveoli.
What are alveolar ducts?
Alveolar ducts are air passages that are lined entirely by alveoli. (Hallway in the hotel!)
What are alveolar sacs?
Alveolar sacs are dead-end clusters of alveoli. Think Fancy suite of rooms at the end of the hall!
Where does gaseous exchange occur?
In the Alveoli!
Blood-air barrier; fused basal lamina
What type of cells are in the alveolar septum?
Endothelial, Type I and II alveolar; interstitial; alveolar macrophages
What are the pores of Kohn and what do they do?
The alveoler pores of Kohn equalize pressure between alveoli. Also allow for areas of communication in alveoli
What is the structure of the alveolar wall? Which is more abundant on the wall Type I or Type II?
Alveoli are lined by simple squamous epithelium (type I pneumocytes) which comprise 95% of the area of the alveolar surface.
What do Type II pneumocytes do?
Type II penumocytes are thicker and contain lamellar bodies. Type II pneumocytes are more common and can reproduce to replace the type I pneumocytes.
Are there more Type II or Type I?
More Type II, around 60% but Type I covers 90% of alveolus surface
What is the function of lamellar bodies?
They produce surfactant to lower surface tension and prevent alveolar collapse
What is the function of alveolar “dust cells”?
These are macrophages that phagocytose particulate matter that might be inhaled.
What is the minimum membrane for gas exchange?
The minimum membrane for gas exchange is the type I pneumocyte, the common basement membrane and the alveolar capillary endothelial cell.
How do the blood vessels distribute to the alveoli?
The arteries travel with bronchi and bronchioles (get oxygenated by alveoli), while the veins travel in the elastic connective tissue septa between lung segments.
What do Parasympathetic nerves do in the lungs?
Parasympathetic nerve fibers (from the vagus) constrict bronchial smooth muscle and increase glandular secretion.
What do sympathetics fiber do?
Sympathetics relax bronchial smooth muscle and decrease secretion.
What are the functions of sensory fibers?
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).
Which cells of the bone marrow can regenerate themselves?
Pleuripotent and multipotent stem cells can reproduce themselves. All other cells are committed to differentiating.
Are blast cells mitotic and self-replicating?
blast cells are mitotic but NOT self-replicating
What are the changes in cell appearance of blood cell precursors as blood cells differentiate?
Cells become smaller; lose nucleoli; develop granules; nucleus assumes a more adult shape.
Which hematopoietic cells have the greatest mitotic activity?
Blast cells are the most mitotically active.
What is self renewal?
Will create another undifferentiated stem cell
What is the primary growth factor that stimulates erythropoiesis and where is it made?
Erythopoietin (EPO): stimulates RBC development and is made in the kidney.
What cells are self-renewing?
Pluripotent stem cells, myeloid multipotent stem cell and lymphoid multipoint stem cell
What do Myeloid multipotent stem cells produce? Lymphoid?
Myeloid Multipotent Stem Cell: Erythrocytic progenitor cells; granulocytic (GM) progenitor cells & megakaryocytic progenitor cells
Lymphoid multipotent stem cells: B lymphocyte progenitor cells and T lymphocyte progenitor cells
What is the most important interleukin to stimulate the production of all myeloid cells and what cells produce it?
IL-3 is producted by T-lymphocytes and stimulates production of all myeloid cells.
What is G-CSF?
G-CSF is produced by macrophages, endothelum and fibroblasts and stimulates granulocyte development.
What is GM-CSF?
GM-CSF is produced by lymphocytes, endothelium and fibroblasts and stimulates both granulocyte and macrophage development.
What is the most important growth factor stimlating production of platelets and where it it made?
Thrombopoietin is produced by the liver and kidney and stimulates the production of platelets.
What is the first site of RBC production? What are the second and third sites?
The yolk sac is the first site, with the liver and spleen following.
In a normal, term infant, what site(s) is/are active in producing RBCs?
Only the bone marrow is producing erythrocytes by the time of birth
In the adult, where would you expect to find red marrow?
Red marrow would be found in vertebra, pelvis, ribs and sternum. Yellow marrow would fill the marrow cavity of long bones.
When does the bone marrow start producing RBCs?
About the middle of fetal life is when the bone marrow start producing RBCs.
What are multipotent stem cells?
Multipotent stem cells can give rise to a more limited progeny (often a single cell line) but they are still able to be self renewing.
What are pluripotent stem cells?
Pleuripotent stem cells can give rise to all types of blood cells (and many other cell types, as well). They can also reproduce into more pleuripotent stem cells.
What are colony forming units (CFUs)?
Colony Forming Units, are progenitor cells that can differentiate into a limited # of cell types (usually just one clone of cells).
What kind of cells would you expect to find in the extravascular compartment of the bone marrow? What kind of fibers?
Bone marrow contains hematopoietic cells, adventitial cells (stromal cells) and fat cells. The great majority of fibers are reticular fibers.
What is meant by a “hypercellular marrow”?
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).
What is red marrow like?
Active marrow; relatively less fat, more cells making blood cells
What is yellow marrow like?
Inactive marrow; lots of fact; has the ability to convert back to red marrow in times of need
What is the structure of the vascular compartment of the bone marrow?
There are venous sinusoids with a discontinuous and fenestrated endothelium.
What is an erythoblastic island and what is at its center?
An erythroblastic island is a cluster of developing RBCs around a macrophage (which appears to recycle iron)
How long does erythopoiesis take?
Erythropoiesis takes about a week.
What are the stages of erythropoiesis from the earliest recognizible stage?
Proerythroblast (least mature) –> Basophilic erythroblast –> Polychromatophilic erythroblast –> Orthochromatophilic erythroblast–> reticulocyte -> Erythrocyte
At what stage does the erythrocyte lose its nucleus, and what happens to it?
Between the orthochromatophilic erythroblast and reticulocyte it is extruded and phagocytosed by the macrophage.
How long does it take a reticulocyte to mature to an RBC? How long do reticulocytes last in the bloodstream?
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.
About what percent of RBCs are reticulocytes?
There are about 1% reticulocytes in the blood because RBCs last for about 120 days in the circulation.
How long does granulopoiesis take?
Granulopoiesis takes about 14 days. During the first week there is rapid reporduction of cells and the second week is dominated by maturation
What are the stages of production of a neutrophil?
Myeloblast --> Promyelocyte--> Myelocyte--> Metamyelocyte--> Band cell--> Mature neutrophil (PMN)
What does an increase in band cells indicate?
It indicates the release of immature PMNs from the bone marrow, often due to increased demand due to infection.
What does the megakaryocyte nucleus look like?
The megakaryocyte nucleus is multi-lobed due to endomitosis.
What is unusual about structure of the megakayocyte (outside of the nucleus)?
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.
What is the approximate ratio between myeloid and erythroid precursors in the marrow?
The myeloid:erythroid ration is about 3:1 in normal marrow.
Which has more mature cells? Bone marrow or blast cells?
Bone marrow has more cells
Will you see stem cells and progenitor cells n the marrow?
No, unless you use cell markers
How do megakaryocytic extend cytoplasmic process into sinuses?
By dynein motors
