MICROSCOPIC ANATOMY Flashcards
components of plasma
- albumin (maintains osmotic P and helps transport water insoluble substances)
- gamma globulins (antibodies)
- fibrinogen (for clotting)
- complement proteins (important for inflammation and destruction of microorganisms)
- other solutes (electrolytes, nutrients, gases, hormones, enzymes)
buffy coat
1% of blood volume and consists of leukocytes and platelets
leukocytes (with percentages and numbers)
total= 6,000-10,000/microliters (approximately 7,500)
neutrophils (60-70%)--> 4,500-5,250 lymphocytes (20-30%)--> 1,500-2,250 monocyte (3-8%)--> 225-600 eosinophil (2-4%)--> 150-300 basophil (0-1%)--> 0-75
what is the shape of a RBC and what does it imply?
biconcave disc without a nucleus maximizing surface area to volume ratio for efficient gas exchange
what is the membrane skeleton of an erythrocyte made out of?
spectrin, actin and protein 4.1
major and minor forms of adult hemoglobin:
major: HBA1 (95%) in which there are 2 alpha and 2 beta polypeptide chains
minor: HbA2 (5%) in which there are 2 alpha and 2 delta polypeptide chains
what are the consequences of sickled erythrocytes?
they are inflexible, have a reduced life span leading to anemia and they increase blood viscosity leading to ischemia
what removes senescent RBCs?
macrophages which are located in the spleen, liver and bone marrow
*RBCs survive for approximately 120 days
reticulocytes
1% of circulating RBCs containing a small amount of rRNA (lost after 1 day of circulation) and are recently released giving a rough estimate of the rate of erythropoiesis
*stains with brilliant cresyl blue
2 classes of leukocytes and how leukocytes function
function as the main line of defense against bacteria, viruses and parasites outside of the blood vessels, leaving by means of diapedesis (between/paracellular or through/transcellular cells)
granulocytes: neutrophils, eosinophils and basophils
agranulocytes: lymphocytes and monocytes
diapedesis
the leaving of blood cells (leukocytes) through capillary walls
neutrophil
- nucleus is heterochromatic and not metabolically active with 2-5 lobes (polymorphonuclear- variable sized) each connected by a thin strand of chromatin
- SPECIFIC granules (makes up 80% of granules and responsible for staining qualities) AND AZUROPHILIC granules (makes up 20% of granules and is large and stained with Azure B with many hydrolytic enzymes to kill bacteria) are present
- few cellular components but a considerable amount of glycogen
- functions: motile, chemotaxis (movement in response to chemical stimulus), and phagocytosis
what are lysozyme and lactoferrin’s functions?
lysozyme: hydrolyzes glycosidases in bacterial cell wall
lactoferrin: iron binding protein
describe the process of phagocytosis by a neutrophil:
- pseudopodia surround bacteria forming phagosomes which then fuse with granules causing hydrolysis of the bacteria
- superoxide (O2-) anions form and netosis occurs (the release of a net-like structure capable of trapping microbes)
- microvesicles that have antibacterial activity are released along with cytokines
- neutrophils die and form pus
eosinophils
bilobed nucleus with SPECIFIC cytoplasmic granules (which have hydrolytic enzymes and a crystalline core) and functions to kill larvae of parasitic worms with EBP, dispose of antigen-antibody complexes and release granule contents (histamine and anaphylaxis substance SRS-A)
*can lead to asthma due to bronchoconstriction, mucus hypersecretion, inflammation and airway remodeling (increased SM, collagen and GC metaplasia)
basophil
less segmented nuclei with many SPECIFIC granules containing heparin, histamine and SRS-A that stain with Azure B
-IgE will bind to its surface stimulating degranulation of it along with mast cells leading to a localized or widespread reaction since they play a role in inflammation and hypersensitivity reactions (could be delayed)
- *shares many cytochemical and pharmacological characteristics with mast cells
- *produces eosinophilic chemotactic factor
lymphocyte types
3 types: small-medium, large agranular and large granular (some have large AZUROPHILIC granules) (large- less heterochromatic) which are all activated by specific antigens
lymphocyte functions
function as: B-cells and T-cells
- B-cells/humoral immunity: (10-15%) differentiate into plasma cells which produce antibodies/immunoglobulins that serve as antigen-receptors on the surface initiating mitosis when stimulated by an antigen (production of plasma cells which make antibodies or memory B-cells which help the cell respond more rapidly to subsequent exposure)
- T-cells/cell-mediated immunity: (70-80%) require APC in order to facilitate the binding of T-cells to foreign antigens stimulating mitosis leading to the production of memory T-cells, cytotoxic T lymphocytes (perforin lyses target cells while granzymes induce apoptosis -FAS-FAS ligand), helper T-cells (which assist B-cells) or suppressor/regulator T-cells (suppresses immune response to self molecules preventing autoimmune diseases)
natural killer cells
large granular lymphocytes which represent 5% of circulating lymphocytes containing azurophilic granules but lacking in B or T-cell surface molecules
- helps kill virus-infected or malignant cells (such as transplanted or foreign cells) through the production of cytokines
- T-cell polarization
monocytes
variable shaped euchromatic nucleus and cytosol containing small AZUROPHILIC granules, vacuoles and alpha-naphthyl acetate esterase (useful marker)
*developed from blasts in the red bone marrow (2-3 days) then remain in the peripheral circulation (1-2 days) migrating to tissues when they have transformed into macrophages/histiocytes function for 1-3 months with the ability of phagocytosis, serving as APC, forming osteoclasts, producing cytokines and monitoring endothelial cells
blood platelets/thrombocytes
fragments of megakaryocytes that are produced in the bone marrow and are non-nucleated with a central darkly staining granulomere, mRNAs and peripheral less intensely staining hyalomere appearing in clumps and lasting for approximately 10 days
- N= 250,000/microliter
- function= “platelet plug”- seals off small breaks playing a role in coagulation since it serves as a surface upon which clotting reactions occur
Romanovsky type stains
2 basic dyes and 1 acidic dye (examples of mixtures: Wright’s, Giemsa, May-Grunwald)
basic:
1. azure B- binds to DNA and glycosaminoglycans staining nuclei purple while staining granules of basophils and lysosomes a crimson color
- methylene blue- binds to RNA and stains the cytoplasm of the cell a heavenly blue
acidic:
1. eosin- stains proteins, hemoglobin and granules of eosinophils a red-pink color
regions of a blood smear
beginning/head: overlap
middle: RBCs are separated and leukocytes are intact (area of choice for study)
end/tail: over-stretched, broken and distorted
lymphoid multipotential cells vs. myeloid multipotential cells
lymphoid: migrate to lymphoid organs
myeloid: remain in bone marrow
hematopoiesis, granulopoiesis and erythropoiesis
development of: blood cells, granulocytes and erythrocytes
*hematopoiesis occurs in the bone marrow, lymphoid organs and in the liver (fetuses)
blasts
precursor cell to one type of blood cell in which it signifies the start of morphological differentiation with high mitotic activity but without the ability to self-renew
- large cell with a large euchromatic nucleus, several nucleoi and many ribosomes surrounded by a blue cytoplasm
- NO granules are present
neutrophilic differentiation and stages
myeloblast–> promyeloblast–> myelocyte–> metamyelocyte–> band cell–> mature pmn
- first 4 in bone marrow and last two in peripheral blood
- chromatin becomes heterochromatic, nucleus becomes lobulated, granules appear and basophilia decreases
neutrophilic promyelocyte
slight chromatin condensation and contains AZUROPHILIC granules and lysosomes (hydrolytic enzymes- acid phosphatase +) and is capable of mitosis
neutrophilic myelocyte
nucleus is round/oval and more heterochromatic containing much more SPECIFIC granules (lacoferrin and lysozyme) and less AZUROPHILIC granules and is capable of mitosis even though ability to replicate DNA and synthesize RNA decreases
- cytoplasmic color change
- chromatin= more condensed and basophilia= decreases
neutrophilic metamyelocyte
- is no longer able to sunthesize nucleic acids (DNA and RNA) or undergo mitosis
- chromatin is more condensed (Golgi is reduced) and it has an indented nucleus without basophilia but with many SPECIFIC and a few AZUROPHILIC granules
neutrophilic band
- *percentage in the peripheral blood is a rough estimation of the rate of neutrophil production
- further bending of the nucleus to look like an “S” without the capability of mitosis and chromatin is condensed
how long does it take for neutrophils to be produced and what is their fate?
production of neutrophils takes 9-14 days and then it is circulated in the peripheral blood in 1 of 2 different pools for one day (exchange of cells between the two can occur):
- circulating pool: suspended in plasma and circulating in vessels
- marginating pool: not circulating meaning in constricted capillaries or adhered to endothelium
then diapedesis occurs (paracellular or transcellular) and the cells can live for 5 days in tissues
distribution of granulocytes:
MGR- marrow granulocytic reserve (bone marrow)
TBGP- total blood granulocyte pool (peripheral circulation)
MGR= 10 x TBGP
red bone marrow
RED BLOOD CELLS
in the flat bones (especially the spongy bone) of the body containing cords of hematopoietic cells for blood cells to mature
- nurtures stem cells and facilitates their activity as a hematopoietic stem cell niche
- alterations–> myeloproliferative disease
yellow bone marrow
ENERGY
collection of adipose cells holding energy located in the medullary cavities of bones (all but flat bones) which are not active during hematopoiesis
erythrocyte differentiation including stages:
decrease in volume–> nuclear changes (chromatin becomes heterochromatic, nucleoli disappear, cell gets smaller and extrusion of nucleus)–> cytoplasmic changes (polysomes decrease and hemoglobin increases)
BLAST/ERYTHROBLAST–> BASOPHILIC ERYTHROBLAST–> POLYCHROMATOPHILIC ERYTHROBLAST–> NORMOBLAST–> RETICULOCYTE–> ORTHOCHROMATIC ERYTHROBLAST–> MATURE ERYTHROCYTE (RBC)
basophilic erythroblast
smaller than the blast lasting 1-2 days with no nucleoli but a checkerboard appearance of chromatin and a BASOPHILIC cytoplasm filled with free ribosomes ready to make globin (staining navy blue)
*capable of 1-2 mitotic divisions
polychromatophilic erythroblast
smaller than the basophilic erythroblast lasting 3 days with chromatin that is further condensed and has shifted from intense basophilia to intense ACIDOPHILIA
increased hemoglobin will bind eosin while the RNA ribosomes will bind methylene blue (causes cytoplasm double staining)
*capable of 3-4 mitotic divisions
normoblast
it is no longer capable of mitosis and is smaller than the polychromatophilic erythroblast with a completely heterochromatic nucleus
*cytoplasm is pink (due to eosin staining of lots of hemoglobin) with a hint of blue (due to methylene blue staining of few polyribosomes)
two fate options of normoblasts:
- (80%) can become a reticulocyte through extrusion of the nucleus and retentnion of a few polyribosomes (1% in peripheral blood giving an estimation of the rate of RBC production)
- (20%) can become an orthochromatic erythroblast through the loss of residual RNA before nuclear extrusion occurs- bright eosinophilic cytoplasm and is not normally released into the peripheral circulation
no matter the fate chosen, they will eventually become erythrocytes
timeline for erythrocyte production
takes a total of 8-9 days of which most of the time is spent in the bone marrow
1-2: basophilic erythroblast
3: polychromatophilic erythroblast
3: normoblast-reticulocyte
1: reticulocyte-erythrocyte transition
what does hypoxia stimulate?
hypoxia (due to hemorrhage, hemolysis, high altitude or compromised pulmonary function) stimulates erythropoietin which increases the rate of mitosis and RNA synthesis in developing RBCs
reticular cell
large pale staining nucleus which serves as the storage place for ferritin with many cytoplasmic processes and ingested material (from phagocytosed extruded normoblast nuclei) that presents antigen to T lymphocytes
- play a trophic role in the maturation of erythrocytes by supplying nutrients and growth factors
- mesenchymal origin and processes wrap around reticular fibers
- erythroblastic islands: polychromatophilic erythroblasts clustered around reticular cells
plasma cells
basophilic cytoplasm with an eccentrically placed nucleus and clock-like distribution of chromatin
blood platelets
differentiate from megakaryoblasts and megakaryocytes (maturation taking 4-5 days) with a homogenous basophilic cytoplasm
-circulate for 10 days and are then destroyed in the spleen and liver
megakaryocytes
have a lobulated nucleus, azurophilic granules, an eosinophilic cytoplasm and increase in ploidy up to 32-64n through the process of endomitosis
*invaginations of plasma membrane in cytoplasm forming peudopods which elongate to form proplatelets and demarcation channels causing the partitioning of cytoplasmic fragments to form platelets that enter discontinuous sinusoids in bone marrow (platelets are released from the ends of bifurcated proplatelets)
lymphocytes
cell size decreases, chromatin becomes condensed and nucleoli becomes less visible also acquiring surface receptors
*lymphoblasts reside in bone marrow and their progeny migrates to the thymus and then acquires T-cell characteristics or stay for a longer period of time and eventually differentiate into B-cells
3 types of host defense
- acid-base balance (regulates CO2 and pH)
- metabolic (activates bradykinin, serotonin, ACh and converts ANG I to ANG II)
- immunologic (cellular-vibrissae, macrophages and muco-ciliary elevator and humoral- IgA and IgE)
air conditioning
inspired air is filtered (to prevent pathogens from coming in), warmed (to prevent tissue damage) and humidified (to enhance gas exchange) by the ciliated pseudostratified columnar epithelial cells of the conducting zone before reaching the respiratory zone
which bronchioles belong to the conducting zone and which bronchioles belong to the respiratory zone?
conducting (gets air in): regular and terminal bronchioles
respiratory (gas exchange): respiratory bronchioles
cell types of conducting and respiratory zones:
conducting: ciliated pseudostratified columnar (top- cilia–> basal bodies–> goblet cells (secretes mucous)–> PSEUDOSTRATIFIED COLUMNAR basal cells–> basement membrane–> elastic fibers–> mucous and seromucous glands)
respiratory: simple squamous to maximize surface area
5 cell types of respiratory epithelium
extend to lumen:
- ciliated pseudostratified columnar epithelial cells
- mucous goblet cells
- brush cells (sensory receptors- afferent nerve endings)
do not extend to lumen:
- basal cells (undergo mitosis to make new cell types)
- granule cells
muco-ciliary elevator
host defense mechanism in which inhaled particles are trapped in mucous secreted by goblet cells and the coordinated beating action of cilia propels the mucous and trapped particles out
Kartagener syndrome
dynein dysfunction preventing cilia from beating in a coordinated fashion thus particles cannot be effectively cleared (increase in respiratory infections)
transitional changes that occur from conducting zone to respiratory zone
ciliated pseudostratified columnar–> ciliated simple cuboidal–> squamous cells (alveoli)
goblet cells, smooth muscle and cartilage decreases
elastic fibers in CT increases
cilia are found deeper in the respiratory tract than goblet cells to prevent retrograde flow of mucous
nasal cavity
- vestibule contains sebaceous(oil) and sweat glands and vibrissae (hair)
- fossae (2 chambers in skull separated by a bony nasal septum) is made up of 3 conchae (projections of bone covered with CT and epithelium and a venous plexus to warm air) and 3 meatus (spaces between conchae for air passage which forces turbulent air flow to humidify and warm air- superior is lined with olfactory epithelium)
olfactory epithelial organization
lines the superior meatus, does not have cilia, has an underlying nerve and is made up of 3 different cells:
- supporting cells: microvilli
- olfactory cells: bipolar neurons with a central nuclei
- basal cells: base of the epithelium
*also has olfactory (Bowman’s) glands which produce proteinaceous serous secretions to facilitate access of new odorants
paranasal sinuses
chambers (frontal, maxillary, ethmoid and sphenoid) lined with respiratory ciliated epithelium, goblet cells and small glands
pharynx
- tube that connects oral and nasal passages
- respiratory epithelium dorsally and squamous epithelium ventrally
larynx
- connects pharynx to trachea
- epiglottis prevents food from entering trachea
- hyaline cartilage–> ossifies as you age which changes voice since near cord (false vocal cords- resp. ep. and true vocal cords- squamous with ligament and muscle)
trachea
- connects larynx to bronchi
- respiratory epithelium
- thick basement membrane
- regular rings of hyaline cartilage
- fibroelastic ligament
bronchi
- irregular cartilage
- 5 branches of the 2 primary bronchi (3 right and 2 left)
- smooth muscle in irregular bands causing wavy/folded mucosa and regulating the size of the bronchi
bronchioles of the conducting zone
-No cartilage but smooth muscle is present
regular: ciliated columnar (or pseudostratified) with some goblet cells and a wavy or folded mucosa
* *site of heaviest ventilation regulation due to large cross-sectional area, lack of cartilage and presence of smooth muscle
terminal: non-ciliated columnar or cuboidal with smooth mucosa and goblet cells are replaced with secretory Clara cells which extend taller, have dense granules and require a special stain
bronchioles of the respiratory zone
-simple cuboidal or columnar with few cilia but no goblet cells
alveolar ducts
simple squamous lacking cilia, goblet cells and Clara cells but has smooth muscle cusps that allow for more regulation of ventilation
alveolar septum the its diffusion pathway
thin wall that allows for gas exchange from air to blood
diffusion path for gases:
- surfactant
- epithelium (2 membranes and sytoplasm)
- fused basement membrane (epithelial and endothelial basal lamina)
- endothelium (2 membranes and cytoplasm)
- RBC membrane
**cells of the alveolar septum (6)
- type I epithelium/pneumocyte: squamous lung lining
- *endothelial, dust, RBC, mast cells, fibroblasts (gas ex.)
- type II epithlium/pneumocyte: cuboidal found at junction
- capillary endothelial cells: thin and crescent shaped (endothelium before RBCs that gases must diffuse through in septum)
- interstitial cells: fibroblasts and mast cells; macrophages aka “Dust cells” originated in bone marrow and critical to host defense
- alveolar pores (Pores of Kohn): equalize air P and promote collateral air circulation
- acellular interstitium: passive exhalation necessities- collagen (type III), elastic fibers and proteoglycans
hilus
where pleura layers fuse (they each contain a mesothelium)
nerves of the respiratory system
sympathetic and parasympathetic to control dilation and are poorly localized pain responses
BALT
- Bronchially Associated Lymphoid Tissues
- dense accumulations of lymphoid tissue
characteristics of a lymphoid tissue
- -loose: open meshwork
- dense: many free cells- lymphocytes
- nodular: aggregates with many lymphocytes
- primary–> tightly packed
- secondary–> contain geminal centers appearing during primary antigenic response and involuting after 4 weeks (inside are B cells that undergo proliferation, selection, apoptosis, differentiation and storage) with 3 distinct zones: dark (proliferation and division of B lymphocytes), light (selection, apoptosis and differentiation into plasma cells and memory B cells) and mantle zones (temporary storage of young plasma cells and memory B cells)
3 types of lymphoid tissue
loose, dense and nodular (primary and secondary
primary and secondary lymphoid organs
primary: bone marrow, thymus
secondary: lymph nodes, spleen, tonsils, Peyer’s patches
* lymphocytes recirculate between these organs and the blood (also allows for rapid response to antigens)
extralymphoids
aggregates of lymphoid tissue in non-lymphoid organs:
- GALT (digestive system)
- respiratory tract
- urinary tract
- reproductive tract
- SALT (skin)
antigen presenting cells
macrophages and dendritic cells
reticular fibers
PAS+, reduces silver salts and is composed of Type III collagen
*form a sponge-like network with reticular cells to support lymphocytes and fit into formed spaces
lymph node structure
- kidney-shaped with an indentation known as a HILUS in which blood vessels enter and blood vessels and efferent lymphatics leave
- capsule: dense irregular CT with trabeculae that provide support and subdivide
- cortex: loose lymphoid tissue
- paracortical zone: site of HEVs and is under the influence of the thymus
- medulla: composed of dense lymphoid tissue and has medullary cords that are densely packed with lymphocytes and differentiated plasma cells and medullary sinuses made of loose lymphoid tissue and has permeable walls for the passage of wandering cells
flow of lymph through nodes
production in germinal centers–> forced to the periphery of nodules–>afferent lymphatics (entrance)–> sinuses (subcapsular, peritrabecular/intermediate, medullary) allowing for slow filtration–> efferent lymphatics (exit)–> enter blood circulatory system via thoracic duct
HEV
- High Endothelial Venules
- located in the peripheral deep cortex unit of the paracortical zone fo the thymus providing a way for lymphocytes to return to nodes (recirculation) which permits communication and the ability to encounter antigens
- decreases as age increases
deep cortex unit of the paracortical zone
central: high amount of lymphocytes, low amount of reticular fibers and is used for cellular storage and proliferation
peripheral: low amount of lymphocytes, high amount of reticular fibers and is the site of HEVs and used for rapid migration of lymphocytes
lymph node function
filtration of lymph, production ad selection of B lymphocytes and *play a role in the immune response to lymph-borne antigens
thymus
contains a capsule (thin dense CT), two main lobes and lobules located in the superior mediastinum and is developed by birth, its maximum size by age 1 and involutes (curls up) by age 2 in which the parenchyma is replaced by fat and fibrous tissue
**dual embryonic origin (mesenchyme and epithelial lining of 3rd and 4th branchial/pharyngeal pouches)
*lobules- contain a cortex (peripherally located staining darker with dense lymphoid tissues and many lymphocytes serving as the site of thymocyte proliferation, apoptosis and selection) and medulla (centrally located staining lightly with loose lymphoid tissue and many reticular cells serving as the site of thymocyte maturation)
cell types of the thymus
- thymocytes: in cortical regions and proliferate/undergo selection in the cortex traveling to other lymphoid organs
- epithelial reticular cells: not phagocytic and originate in endodermal lining of 3rd and 4th branchial pouches and do not manufacture reticular fibers but prevent T-cells that would cause autoimmunity from surviving and have a secretory function producing thymosins and thymopoietin; desmosomes and tonofilaments help with their structure
- forms Hassall’s corpuscles arranged concentrically and frequently keratinize/ossify decreasing in number but increasing in size with age
- contributes to the blood-thymus barrier (immunologically privileged site for differentiating thymocytes and protects cortical lymphocytes from circulating antigens
-reticular cell of mesenchymal origin (dendritic cells): phagocytic to clean up debris resulting from T cell selection and provides a microenvironment with thymosin and thymopoietin to support the development of T cells
thymosins and thymopoietin
- both are produced by the epithelial reticular cells of the thymus due to their secretory function
- thymosins: promote differentiation of disease-fighting T lymphocytes
- thymopoietin: has a trophic action (growth effect) on the lymphoid system
spleen function and structure
largest accumulation of lymphatic tissue in the body that filters the blood composed of a dense irregular CT capsule, trabeculae that provides support and contains blood vessels, a small amount of smooth muscle and splenic pulp
- destroys old RBCs and is a reservoir of monocytes producing lymphocytes in germinal centers of secondary lymphatic nodules which plays a role in the immune response to blood-borne antigens
- activated B cells do to lymphatic nodules where as activated T cells migrate to PALS to become cytotoxic, helper, suppressor or memory T cells
splenic pulp
red pulp: (80%) contains blood and is made up of splenic sinuses (irregular vascular channel with elongated endothelial cells, macrophages and a discontinuous basement membrane) and splenic cords (plates of cellular tissue lying between–> functions to destroy old RBCs and stores blood
white pulp: (20%) composed of lymphoid tissue, PALS (periarterial lymphatic sheath that surrounds arterial branches and is a T dependent area) and lymphatic nodules (contains B lymphocytes and may have germinal centers)
**marginal zone: at the junction of red and white pulp with arterial blood containing lymphocytes, dendritic cells and macrophages serving as the site if initiation of immune responses to blood-borne antigens
*blood flow through the spleen
entrance at hilus–>
splenic artery–>
trabecular arteries–>
central arteries (arterioles in the periarterial lymphatic sheaths and lymphatic nodules supplying the lymphatic tissue and marginal zone)–>
penicillin (straight branches into red pulp)–>
capillaries (open (capillaries to cords to sinuses-slow) and closed (capillaries to sinuses-faster) theories of splenic circulation)–>
splenic sinuses (wide channels in spaces between endothelial cells with a discontinuous basement membrane allowing free exchange)–>
exit through: red pulp veins, trabecular veins and splenic veins
4 fates of activated T cells
- cytotoxic
- helper T
- suppressor
- memory T
tonsils
aggregates of dense lymphoid tissue with nodules and many germinal centers that lie beneath an epithelium in the upper pharynx reaching maximal development in childhood and function to detect and respond to pathogens in the oral cavity through its production of lymphocytes
3 types of tonsils
- palatine/paired: lateral walls of the oropharynx surrounded by a thick capsule of dense irregular CT covered by stratified squamous epithelium that invaginates to form deep crypts that contain desquamated epithelial cells, lymphocytes and bacteria
- pharyngeal/adenoids: roof of the nasopharynx surrounded by a thin capsule of dense irregulat CT covered by pseudostratified ciliated columnar epithelium with folds/pleats
- lingual: base of the tongue associated with its mucous glands and skeletal muscle; smaller and more numerous than other tonsils with stratified squamous epithelium and a single large crypt filled with detritus
