Exam III Flashcards
What is the musculature of the GI tract?
- skeletal muscle at either end
- smooth throughout rest
What is intrinsic rhythmicity in terms of the GI tract?
- due to presence of enteric nervous system
- receives input from sympathetic and parasympathetic
What are the peptide neurotransmitters present?
- bombesin
- motillin
- vasoactive intestinal peptide
What are the GI unicellular endocrine cells?
- secretes neuropeptides
- derived from endoderm
What is the lymphatic tissue found in the GI?
-MALT (mucosal associated lymphoid tissue)
+GALT in gut
What are the protective mechanisms in the GI?
-production of mucus
rapid turnover of epithelial cells in harsh environments
Describe lip histology.
- lined with mucus membrane lying on vascular FECT -> stratified squamous
- composed of core of skeletal muscle (orbicularis oris)
- internal poorly keratinized, modified, stratified squamous epithelium lies on lamina propria with high papillae
- mixed and mucus glands in lamina
- dermis has rich plexus of capillaries
Histology of cheek.
-structure similar to lip
-abundant elastic fibers in submucosa
+allows for maximum distensibility to oral mucus membrane
What are the three embryonic tissues used to develop the teeth?
-ectoderm -> enamel
-neural crest
-mesoderm
+both form dentin, cementum, and pulp
How are teeth developed?
- dental primordium formed from basal cells of ectoderm
- labiodental lamina is an epithelial shelf that grows the thickened primordium into mesenchyme as a bifid structure
- external limb splits later to form a groove that deepens to separate the lip and the remainder of the mouth
- internal limb is dental lamina
- cells proliferate to form the tooth bud
- later, a second set of tooth buds develops on the lingual side of each developing deciduous tooth -> permanent teeht
What is the enamel organ?
forms enamel and caps dental papillae
What is the dental papillae?
-condensation of mesenchyme that gives rise to dentin and pulp
What is the dental sac?
-CT sac that surrounds the enamel organ and dental papilla and forms cementum and peridontal membrane
What are the cells found in tooth development?
- odontoblasts
- ameloblasts
What do the odoontoblasts do?
-form dentin matrix throughout life of tooth
-form single layer of cells lining pulp cavity
-Tomes dentinal fibers
+occupy dentinal tubules
+cyutoplasmic extensions of the odontoblasts continuing through the predentin and dentinal layers to the dentin-enamel junction
-increment lines
What is the composition of dentin?
- 20% organic matrix
- composed mostly of type I collagen
What do ameloblasts do?
-forms enamel
+enamel is laid down in prisms -> one per ameloblast
What is the hardest substance in the body?
enamel
What are increment lines of Retzius?
-periods of rhythmic growth
What is removed after calcification in enamel?
- amelogenins
- enamelins
How does pulp develop?
- originates from dental papilla containing condensed mesenchyme
- consists of fibroblasts, macrophages, peripheral odontoblasts, reticular fibers, nerve fibers, and blood vessels
How does cementum form?
- cells of dental sac differentiate into cementoblasts which deposit cementum on the dentin of the root
- has Sharpey’s fibers
How is the periodontal membrane formed?
-CT formed from dental sac with fibroblasts, osteoblasts, cementoblasts, collagen fibers, blood vessels, and nerve fibers
-highly metabolic
-binds cementum to bony socket
-Sharpey’s fibers extend from cementum to alveolar wall
+allows for limited movement
-absorbs pressures of mastication and prevent pressure from damaging alveolar bone
-affected by diabetes and scurvy
Histology of tongue.
- composed of skeletal muscle, glands, and mucus membrane
- ant. 2/3 of upper oral portion is separated from post. 1/3 by sulcus terminalis
- have lingual papillae
What are the four types of papillae?
- filiform papillae
- fungiform papillae
- foliate papillae
- circumvallate papillae
filiform papillae
- most numerous, conical
- eveny distributed over entire oral upper portion
- lack taste buds
fungiform papillae
- few in number
- mushroom appearance
- interspersed singly among the parallel rows of filliform
- taste buds present only on oral surface of the epithelium in contradistinction to the position of the circumvallate
foliate papillae
- rudimentary in humans, but well developed in lower animals
- pharyngeal portion is free of papillae but contain lingual tonsils
circumvallae papillae
- located along sulcus terminalis
- taste buds present on lateral wall
- ducts of von Ebner’s glands (serous)
What are the taste buds?
- sustentacular cells
- taste cells
What are the sustentacular cells?
-spindle shaped support cells and arranged like barrel staves to surround the inner taste pore at the base
What are taste cells?
-long and slender cells with elongated central nucleus and terminates as a short taste hair -> outer taste pore
-possess apical microvilli with taste receptors
distributed between supporting cells
How is taste differentiated? Not including bitter
-different signal transduction pathways
-salt and sour utilize ionic transport as signal transduction mechanism
+sour involves hydrogen ion blocjage of K+ channels to cause depolarization
How is bitter tasted?
- involves hypopolarized state similar to retinal cell signal transduction -> sweet is hyperpolarized
- involves gustucin
- activation of G subunit, decrease in cGMP, and closure of Na+ channels and hypopolarization of the taste cell
What are the 4 layers of the digestive tube?
- epithelium
- lamina propria
- muscularis mucosa
- submucosa
What epithelium are found in the GI tube?
- stratified squamous transitioning to simple columnar
- function dependent on position
Composition of lamina propria
- loose areolar CT
- glands and GALT
histology of muscularis mucosa
-made up of three layers of smooth muscle
histology of submucosa
- dense, irregular CT
- vascularized
- contains nerve plexus, Meissner’s plexus
What is the epithelium of the G tract?
- stratified squamous at the ends
- simple columnar most of the length
- glands along the length
Difference between innate and acquired immunity.
Innate:
- lacks immune response and specificity
- response -> inflammation
- neutrophils are first responders
Acquired:
- develops in response to antigens
- more powerful than innate immunity
- longer to develop
- displays specificity and memory
Passive vs active immunity
passive: temporary immunity due to donated antibodies (transplacental)
active: long lasting/permanent immunity due to self exposure to antigen resulting in memory T cells and B cells specific for antigen
Cell mediated vs humoral immunity
cell mediated: T cells, B cells, and antigen presenting cells
humoral: antibody mediated, plasma cells
What is primary vs secondary lymphoid tissue? Examples of each
Primary: precursor cells that mature into immunocompetent cells. Each cell is programmed to recognize a specific antigen. Ex. thymus and bone marrow
Secondary: trapped antigens stimulate clonal expansions of mature T and B cells. Ex. lymph nodes, spleen, tonsils
Lymphocytes originate in _________ and then take up residence in ____________.
primary lymphoid organs, secondary lymphoid organs
Lymph follicles
- not enclosed within a capsule
- occur singly or in aggregates
- are sites of B cell localization and proliferation
- transient
primary vs secondary follicles (nodules)
primary: spherical, tightly packed accumulations of virgin B cells and dendritic reticular cells that have not been exposed to antigens
secondary: are derived from primary follicles that have been exposed to nonself antigens, not present at birth
In a lymph follicle the _______ is the darker peripheral region composed of densely packed ___ lymphocytes.
The central, light region is called the __________ and is composed of ________, _______, _________, and __________.
corona, B
germinal center, B lymphocytes, memory B cells, plasma cells, and dendritic reticular cells (antigen presenting)
How are lymphoid follicles vascularly supplied?
-corona and germinal center are supplied by independent arterioles and venules
Where are diffuse and aggregated lymphoid tissue located?
diffuse: located in CT stroma and various other sites (plasma cells, macrophages, and lymphocytes)
+subcutaneous associated lymphoid tissue is found in the papillary layer of the dermis
+lamina propria associated lymphoid tissue
1. MALT
2. BALT
3. GALT
aggregated: beneath and in contact with epithelium (includes tonsils and Peyer’s patches in ileum)
Where do immune cells originate?
bone marrow
Where do T cells travel? B cells?
- thymus
- lymphoid tissue
Maturation of B cells involves what receptors?
- IgM and IgD
- MHC class II proteins
- complement receptors
- Ig Fc receptors
What are the 5 classes of antibody? Antibody structure?
5 classes:
IgA, IgD, IgG, IgG, IgM, IgE
Structure: -light and heavy chains -highly variable regions: \+Fab fragment -> recognizes antigen -less variable region: \+Fc -> bonds antibody to cells
Where are the antibodies found?
IgA: saliva, milk, GU, and respiratory
IgD: surface of B cells
IgG: major Ig in blood, most antibody activity
IgE: allergic responses
IgM: first antibody class expressed by developing B cells
What is the major histocompatibility complex? Classes MHC genes?
-main function of MHC gene products is the presentation of antigenic peptides to T cells
MHC I: expressed on the surface of all cells except trophoblast and RBCs
MHC II: expressed on the surface of the B cells and antigen presenting cells
CD8+ T cells recognize ________ fragments of foreign proteins bound to ______ on the surface of cells.
CD4+ cells also recognize _______ fragments of foreign proteins bound to the _________ on the surface of APCs
- peptide
- MHC class I
What are CD8+ T cells?
- cytolytic T cells
- bind to antigen presenting cells
- undergo mitosis
- release perforins and Fas ligand
- recognize antigens bound to MHC class I
- mediators of cellular immunity
What do CD16+ T cells do?
-natural killer cells
-activated to tumor cell antigens and release cytokines
+interleukin-2 (proliferates NK cells)
+interferon-gamma (activates NK)
+macrophage activating cells
+chemotactic factor
+tumor necrosis factor
How is T cell mediated immunity activated?
-macrophage phagocytizes material and breaks it down into fragments including antigenic properties (epitopes)
-antigens are expressed on surface of macrophage bound to MHC II
-MHC II/antigen complex is presented to helper T cell
-activated T cell undergoes mitosis
+daughter cells will either become memory cells or secrete interleukins
-T cells attract B cells
- B cells access free antigens and undergo mitosis
+some daughter cells become plasma cells (secrete antibodies) and some are memory cells
What is the complement system and what are the two pathways for it?
-an array of about 20 serum proteins which are synthesized in the liver and found in the blood
- classic pathway: cascade activated by antibody binding to pathogen
- alternate pathway: cascade activated by the pathogen
The complement system facilitates _________ and involves ________ the pathogen with complement initiating the cascade.
- inflammatory response
- coating
Where does C1q bind?
Fc region of Ig
->activates C1r and C1s, initiating complement cascade
What does the complement cascade result in?
- activation of membrane attack complex (MAC) on the pathogenleading to perforations and lysis
- production of opsonins, which coatings that make the antigens more palatable to phagocytes
- release of chemotactic agents which attract phagocytes to areas of inflammation of infection
Parenchyma vs stroma
parenchyma: consists of cells that typically pack areas of the lymphoid organ -> lymphocytes
stroma: consists mostly pf reticular fibers and cells, including undifferentiated cells and fixed and free macrophages
What is the hilus of the lymph node?
-entry and exit point for vessels (afferent lymphatic vessels enter the convex side of the node)
What is the capsule of the lymph node composed of?
-dense collagen fibers, elastic fibers, and smooth muscle fibers
How many layers does the cortex of the lymph node have? What is inside each?
- outer (lymph folicles)
- deep (contains T cells, macrophages and endothelial venules (port of entry for circulating differentiated lymphocytes to seed lymph nodes)
What layers do primary and secondary follicles have?
primary -> neither mantle nor germinal center
secondary -> mantle and germinal center
What is in the medulla of the lymph node?
-irregular arrangement of loose medullary sinuses and dense medullary cords
+sinuses are lined with macrophages
+cords consist of blood vessels, lymphoblasts, and plasma cells
-site of lymphocyte reentry into lymph stream
-thymic-dependent areas in subcortical and deeper medullary regions
Histology of the thymus
capsule:
- blood vessels
- no lymph vessels
- extends trabeculae into the parenchyma
trabeculae:
- delicate CT
- divide the thymus into incomplete lobules
lobules: outer, darker staining cortex and inner, lighter staining medulla
- > cortex
- cell population (reticular cells (thymosin) and T cells in various stages of differentiation
- thymocytes migrate from cortical areas to medullary areas
- blood vessels surrounded by continuous epithelial barrier (maintain lymphopoiesis while segregated from antigens)
- >medulla
- specialized to aloow entry channel into blood of mature lymphocytes
- capillary beds not sheathed by epithelial cells
What are Hassall’s corpuscles and where are they found?
-found in medulla of lymph nodes
-whorls of highly keratiized medullary epithelial cells -> produce thymic stromal lymphopoietin
+stimulates thymic dendritic cells needed for the maturation of single positive T cells
The thymus is most developed at _________ and contains no ___________, _________, ___________
- puberty
- lymph follicles
- afferent lymph vessels
- lymph sinuses
Difference between double negative, double positive, and single positive T cells
double negative:
- lack cell surface molecules typicale of mature T cells
- enter cortex from blood vessels
- proliferate in subcapsular area
double positive:
- confronted with epithelial cells with cell surface MHC classes I and II for clonal selection
- express both CD4 and CD8 coreceptors and TCR receptors
single positive:
-express TCR receptors and either CD4 or CD8
What is Foxn-1 and Aire?
- both are transcription factors
- Foxn-1: essential for differentiation of thymic epithelial cells
- Aire:promotes the expression of a portfolio of tissue specific cell proteins by thymic medullary epithelial cells
-these proteins permit the ID and disposal of autoreactive T cells
The blood-thymus barrier is located in ___________ and ______ in the blood from reaching developing ________.
Leaky during __________ life to allow fro development of immunologic tolerance to self-antigen.
- thymic cortex
- prevents antigens
- T cells
- fetal life
What are the functions of the spleen?
blood filtering functions:
- stores and removes worn out RBCs
- recycles iron
- converts hemoglobin to bilirubin
- blood formation in fetus
immunologic functions:
- screens foreign material in the blood
- produces lymphocytes and plasma cells
- removal leads to overwhelming bacterial infections in infants, children, and young adults
What is the white pulp of the spleen?
- elongated, branched strands always associated with arteries
- zones of diffuse lymphoid tissue and germinal centers
- site of clonal expansion of antigen-stimulated lymphocytes
- B cell area contains secondary follicles in which central arteiole is off center
- T cells are found in the areas surrounding the central artery near the center of the white pulp -> FORMS PERIARTERIAL LYMPHATIC SHEATH (PALS)
- reticular fibers are associated with fixed macrophages and support splenic pulp
Histology of marginal zone
- forms sinusoidal interface between red and white pulp
- has abundance of antigen presenting cells
- lymphocytes first encounter antigens here
- activated T helper cells activate B cells
Histology of red pulp
-surrounds white pulp and makes up 80% of spleen
-filters blood
-billrot cords form red pulp parenchyma
+macrophages destroy worn-out defective RBCs
-venous sinusoids
+storage sites of healthy RBCs
What are the functions of the integument?
- protect from mechanical injury
- prevents desiccation
- protects against foreign substances and microorganisms
- protects against UV radiation
- thermoregulation
- regulation of bp
- excretion of metabolic wastes
- synthesis of vitamin D
What is the general organization of the integument?
- epidermis
- basement membrane
- dermis
- subcutaneous tissue
- epidermal ridges
Primary dermal ridges? Interpapillary peg? Secondary dermal ridges? Dermal papillae?
primary dermal ridge:
- related to finger prints
- everywhere except forehead, external ear, perineum, and scrotum
- formed during 3rd-4th month of fetal life
- subdivided into two secondary dermal ridges by interpapillary peg
interpapillary peg:
-downward growth of epidermis along crest
secondary dermal ridges:
- occur in double rows, branched
- thin, collagenous, reticular, and elastic fibers
dermal papillae:
-upward projections from each secondary ridge
What are the layers of the epidermis?
deepest -> superficial
- stratum basale (germinativum)
- stratum spinosum
- stratum granulosum
- stratum lucidum
- stratum corneum
What is the difference between thin and thick skin?
- thick skin occurs only on palms and soles -> hairless
- contains stratum lucidum
What two layers make up the stratum Malpighi?
- straum basale
- stratum spinosum
Histology of stratum basale
-columnar to high cuboidal keratinocytes
-keratins 5 and 14
-single layer of cells
-high mitotic activity
+stems cells -> affected by radiation and chemo
Histology of stratum spinosum
- polyhedral shaped cells (prickle)
- keratins 1 and 10
- keratohyalin granules develop
- tonofibrils (intercellular bridges)
Histology of stratum granulosum
- multilayered
- keratins 2e and 9
- flattened nucleated keratinocytes
- keratohyalin aggregates (cross linkage by disulfide bonds)
- membrane coating granules
- tonofilaments
Histology of stratum lucidum
- flat keratinocytes lacking nuclei and organelles
- contains eleiden
Histology of stratum corneum
- multilayered
- thicker in thin skin
- enucleated, flattened, dead keratinocytes
- cytoplasm replaced by keratin
- cytoplasm contains cross linkages with filaggrin
Histology of extracellular and intracellular cornified cell envelope
extracellular:
-multi-lamellar lipid layer covalently linked to involucrine
intracellular:
- involucrine
- small proline-rich proteins
- loricrin
- fillagrin and keratin complexes
Dermis characteristics
- dense fibrous irregular CT
- mesoderm
- induces development of epidermis and epidermal derivatives
- supports epidermis
Characteristics of hypodermis
- loose CT
- corresponds to superficial fascia
- not technically part of skin
- may contain fat cells that can form a thicker layer called the panniculus adiposus
What are the two layers of the dermis?
papillary (closest to epidermis)
- loose CT
- separated from epidermis by basal lamina
- elastic fibers and abundant capillaries
reticular:
- dense irregular CT
- fibrocytes, macrophages, and adipocytes
Langerhans cells
- dendritic cells
- from monocytes
- antigen presenting cells
- primarily in stratum spinosum
- migrate from epidermis to lymph nodes
Merkel cells
- mechanoreceptors
- may also act as diffuse neuroendocrine cells
- usually in stratum basale
- contain catecholamine-like granules
Melanocytes
- derived from melanoblasts
- don;t form desmosome attachments in epidermis
- inject melanin granules into keratinocytes