Test 4-1 Flashcards
functions onf resp system
air conduction, filtration and gas exchagne
each terminal bronchiole and its respiratory bronchiloar branches supply…
a pulmonary acinus
each respiratory bronchiole supplies a
respiratory bronchiolar unit (aka primary pulmonary lobule)
extrapulmonary airways
- Nasal vestibule and cavity
- Nasopharynx and oropharynx
- Larynx
- Trachea and primary bronchi
intrapulmonary airways
- Secondary (lobar) bronchi
- Tertiary (segmental) bronchi undergo approximately 20 successive divisions. The smallest and last branch is the terminal bronchus.
- terminal bronchus gives rise to primary (lobular) bronchioles.
- Each terminal bronchiole and its respiratory bronchiolar branches supply a pulmonary acinus.
respiratory airways
- Each respiratory bronchiole supplies a respiratory bronchiolar unit (aka primary pulmonary lobule).
- Alveolar ducts
- Alveolar sacs
- Alveoli
brionchiole (lobular) supplies:
secondary pulmonary lobule
terminal bronchiole supplies:
pulmonary acinus
respiratory bronchioles supplyL
primary pulmonary lobule (respiratory lobule)
anthracosis
shows secondary pulmonary outlines - macrophages have eaten carbon ad move into the lymphatics which run in the septa… can see each secondary pulmonary outline
olfactory epithelium epithelium and residents
-pseudostratified columnar w/ cilia
- olfactory receptor cells: axons penetrate the lamina propria and basal lamina; unmyelinated and w/ its own special supporting cell=??
- sustenacular cells: columnar, support and nourish the bipolar receptor cells; lipofuscin granules present
- brush cells: strited brush border; sensory; CN V
- basal cells: short pyramidal shaped on basement membrane; stem cell population that turns into other 3 cells times
larynx epithelium
- stratified squamous non keratinized - subject to vibration and abraision - epglottis and over true vocal chord
- pseudostrat columnar w/ goblet cells - below epiglottis to false to start of true vocal chord and then below true vocal fold down
glands in false vocal folds are:
seromucous glands - mucous durp. - lubrication of lining
reinkes space:
is that part of the lamina propria lying between the basal lamina and the vocal ligament.
edema accumulates in this space
lamina propria of olfactory epithelium contains
- bowman’s glands-serus product contains odorant binding protein
- unmyelinated nerve fibers and bundles
- swell bodies:
psuedostratified epithelium of larynx is also called and is important for:
respiratory epith and mucociliary clearance
vocal folds, anterior surface of epiglottis, and exterior laryngeal surfaces are covered by
non-keratinized, stratified squamous epithelium.
vocal ligament is found
in the lamina propria overlying the vocalis muscle of the true vocal cord
Cellular epithelial residents of the airways are
- Diverse in the larger airways; less diverse in the small airways
- Nonepithelial cells may also be found – Mast cells and intraepithelial lymphocytes (mainly T cells) in larger airways
wall layers of trachae and primary bronhcus
- mucosa
- submucosa with glands
- cartiallage (and treachealis)
- adventitia
wall layers of intrapulmonary bronhci
- mucosa
- muscularis
- submucosa with glands
- cartilage
- adventitia
wall layers of bronchioles
- mucosa
- muscularis
- fibroelastic CT layer
layers of the trachae and extrapulmonary bronchi
1) mucosa
2) submucosa
3) cartilage
4) adventitia
mucosa of trachae and extrapulmonary bronchi
1) Respiratory epithelium supported by a prominent basement membrane
- Ciliated columnar cells are the drivers of mucociliary clearance
- Goblet cells extend from the trachea) to the small bronchi; normally absent in small bronchioles.
- Goblet cells increase in number and extend into the bronchioles when irritated.
- Brush cells have microvilli and have a sensory receptor function
- Basal cells are regenerative cells
- Neuroendocrine cells (of Kulchitsky) – are most numerous in fetal lungs then decrease substantially after birth. Proliferate in certain diseases of the pulmonary system.
- Intraepithelial lymphocytes (mainly T cells)
- Mast cells
2) Lamina propria
submucosa of trachae and extrapulmonary bronchi
- Connective tissue is slightly denser than the lamina propria
- Contains seromucous glands that are responsible for secreting mucins, bacteriostatic substances lactoferrin and lysozyme, IgA produced by plasma cells, and protease inhibitors (e.g., α1-antitrypsin) to degrade proteases released by leukocytes.
A deficiency of α1-antitrypsin leads to
the development of a form of emphysema. (submucosa of trachea/extraplmo branches
cartilage of trachae and extrapulmonary bronchi
- C-shaped rings of hyaline cartilage in the trachea and primary (extrapulmonary) bronchi. -Smooth muscle bridges the ends of the rings.
- Intrapulmonary bronchi contain discontinuous plates of cartilage
adventitia of trachae and extrapulmonary bronchi
fourth layer.
layers of intrapulmonary bronchi
- –> Mucosa – layer 1
- Epithelial cell height decreases as bronchi divide and become smaller
- Basement membrane becomes less conspicuous until it is no longer discernable with a light microscope
- Lamina propria
—> Muscularis of smooth muscle is a new layer – layer 2
- —>Submucosa – layer 3
- Cartilage exists as plates or islands – layer 4
—->Adventitia – layer 5
Asthma and chronic bronchitis
- cause remodeling of the walls of bronchi and bronchioles
- increased mucous production**
- Basal lamina becomes thicker**
- Edema and inflammation of the wall= inc in lamina propria thickness **
- Leukocytes are numerous.
- inc in thickness of muscularis**
- increase in glands of submucosa**
- Hypertrophy and hyperplasia of submucosal glands and goblet cells are more numerous
- Hypertrophy and hyperplasia of smooth muscle cells
layers of bronchioles
1) Mucosa
2) Smooth muscle
3) Fibroelastic CT layer - Elastic fibers maintain the patency of bronchioles - keep from collapsing
- submucosa, submucosal glands, and cartilage are absent in bronchioles
mucosa of bronchioles (terminal)
1) Cellular residents of epithelium rest on a basal lamina:
- Respiratory epithelium in large bronchioles. The epithelium progressively diminishes in height and is simple cuboidal in respiratory bronchioles. The cells are ciliated, though some of the cuboidal cells are non-ciliated.
- Goblet cells are present in large bronchioles; absent in small bronchioles. Goblet cells increase in number and extend into smaller bronchioles with chronic irritation.
- Club (Clara) cells are present in terminal and respiratory bronchioles.Secrete surfactant (differs in chemical composition from that of type II alveolar cells); produce club cell protein (CC 16). CC 16 is increased in the blood and decreased in bronchoalveolar lavage fluid when bronchioles are damaged. CC 16 is an antioxidant/anti-inflammatory molecule. Club cells also regulate Cl- transport. Club cells divide to replace bronchiolar and alveolar epithelial cells.
- Brush cells and neuroendocrine are present in small numbers
2) Lamina propria – glands are absent
what cells secrete surfactant and what layer of what?
club cells in mucosa of bronchioles
goblet cells are present in what and absent in what?
present in large bronchioles
absent in small bronchioles
histology of respiratory surface:
Delicate thin-walled alveoli are associated with respiratory bronchioles, alveolar ducts, and alveolar sacs
-alveolar cells - epithelial type I & II; alveolar macrohages;
alveolar epithelial cells :
1) Type I alveolar cells (pneumocytes)
- represent about 40% of the epithelial cell population but line over 90% of the alveolar surface area
- THIN Simple squamous cells that are attenuated to facilitate gaseous diffusion between blood and alveolus. Type I cells are connected to one another by tight junctions.
- Not capable of cell division
2) Type II alveolar cells (pneumocytes)
- More numerous than type I cells (about 60% of the population) but contribute less than 10% of the alveolar surface area
- ABLE TO DIVIDE in to type I and II
- PLUMP Cuboidal cells with short apical microvilli and connected to type I cells by tight junctions.
- lamellar bodies that contain its secretory product, pulmonary surfactant. Surfactant is composed principally of the phospholipids, dipalmitoyl phosphatidylcholine and phosphatidylglycerol and four surfactant proteins (A, B, C, and D).
3) brush cells
Surfactant
- produced by type II epithelial cells 20-22 weeks
- continuously produced as it is turned over by the endocytotic action of type II pneumocytes and alveolar macrophages via reseptor mediated endocytosis
inducer of surfactant synthesis
cortisol - for respiratory distress syndrome in premautre babies
Inadequate surfactant production causes the lungs to
collapse (atelectasis)
inhibitor of corticosterioids=
insulin
-hyperinsulinemia in fetuses of diabetic mothers leads to a higher incidence of respiratory distress syndrome.
Alveolar macrophages (dust cells)
- Found in the alveolar lumen and migrate over the epithelial surface.
- Also found in the connective tissue compartment of the interalveolar septum.
- Most migrate into the ciliated portions of the airways where they are eliminated by mucociliary clearance
- Some migrate to the connective tissue of the lung beneath the visceral pleura. Black speckled appearance.
- Activated macrophages release proteases that are normally kept in check by antiproteases (e.g., α1-antitrypsin). Genetic deficiency of α1-antitrypsin leads to a form of emphysema.
- Heart failure cells - macrophages that eat RBC and are full of hemosiderin bound to iron
Interalveolar septum
1) Space between adjacent alveolar epithelium
2) Contains continuous capillary or, in wider areas, type III collagen and elastic fibers.
3) Blood-gas barrier
- Type I pneumocytes with adluminal surfactant
- Fused basal laminae of type I pneumocyte and continuous capillary
- Endothelial cells of continuous capillary
three types of bronchioles in order…
lobular bronchiole (goblet cells) —> terminal bronchile —> respiratory bronchioles (no goblet cells)
club cells foudn in
terminal and respiratory bronchioles
if damage to bronchiole epithelial =
increase in CC16 protein
3 mucosa of oral cavity
masticatory - abrasive area
lining
specialized
masticatory muscoa
1) Located on gingivae and hard palate
2) Keratinized and parakeratinized stratified squamous epithelium
3) Lacks a submucosa on gingivae (gums) and palatine raphe
4) Submucosa is found on hard palate: \
a) Anterior submucosa contains adipose CT
b) Posterior submucosa contains mucous glands
c) Collagen fibers anchor mucosa to periosteum of hard palate
5) Burton’s line – blue-gray gingival margin due to lead poisoning
lining mucosa
- Most of oral cavity is lined by this type
- Nonkeratinized stratified squamous (may be parakeratinized in some locations-WITH NUCLEUS): Stratum basale; Stratum spinosum; Stratum superficiale
- Submucosa: Present except on inferior surface of tongue; Contains minor salivary glands and collagen and elastic fibers
Specialized mucosa
associated with taste (gustation)
tongue surface components
1) Filiform: Smallest and most numerous; Elongated, conical projections of connective tissue covered by keratinized stratified squamous epithelium; Only type of papilla to lack taste buds
2) Fungiform: Mushroom-shaped projections covered by stratified squamous epithelium with taste buds; More abundant at tip of tongue
3) Circumvallate; Eight to twelve large papillae surrounded by a moat located anterior to sulcus terminales; Taste buds are located in the stratified squamous epithelium; Lingual salivary glands (von Ebner’s glands) empty their serous secretions into the moat’s base
4) Foliate: Covered by stratified squamous epithelium with taste buds and located along lateral sides of tongue; Small serous glands empty into clefts
taste buds
-Taste pore=Three cell types:
A) Neuroepithelial (sensory) cells
1. Apical surface contains microvilli. Tastants bind to a taste receptor (TR 1 or TR 2). The TR1/2 is associated with a G protein complex called gustducin. The alpha subunit activates GTP which results in depolarization. The influx of Ca ions causes release of neurotransmitters.
2. Connected to neighboring cells via tight junctions and form synapses with CN VII, IX and X
3. Turnover every 10 days
B) Supporting cells:
1. Contains microvilli and tight junctions but do not form synapses
2. Turnover every 10 days
C) Basal cells are located near basal lamina and serve as stem cells
three regions define the lip:
skin, vermilion zone, and mucosa
skin of lip
stratified squamous, keratinized epithelium with hair follicles and glands (sweat and sebaceous). Dermis lies deep to epithelium
vermilion zone of lip (red free margin)
- thin skin that allow the redness of blood to be visible.
- Lacks hair follicles and sweat glands
mucosa of lip
- wet stratified squamous, nonkeratinized epithelium with a lamina propria.
- submucosa lies deep to the mucosa and contains labial salivary glands
major salivary glands
parotid
submandibular
sublingual
parotid gland
- Compound acinar gland
- Purely serous ****
submandibular gland
- Compound tubulo-acinar gland
- Mixed (serous and mucous) though serous predominant****
- Serous demilunes are present
sublingual gland
- Compound tubulo-acinar gland
- Mixed though mucous predominant**
- Serous demilunes are present
[aquired] pellicle is
protective coat on teach made up of proteins in saliva
Layers of a tooth
1) Enamel (covers anatomic crown; absent at root)
2) Dentin (present in crown and root)
3) Cementum (covers root; absent at anatomic crown)
4) Pulp cavity in center w/ nerves and BV
anatomic crown=enamel and dentin
root = cementum and dentin
enamel
- Acellular mineralized tissue that is 96-98% calcium hydroxyapatite – hardest substance in the body (In contrast, mineralized components make up 65% of bone)
- Enamel is derived from epithelial tissue (in contrast to bone which is derived from mesenchyme) and is not replaced after it is formed
- Composed of enamel rods (rods contain calcium hydroxyapatite crystals) that span the entire thickness of the enamel layer
- Mature enamel contains very little organic material (bone is composed of 35% organic material). Enamelins and tuftelins are the protein components.
- Even though enamel is the hardest substance in the body it is subject to the corrosive damage of acid produced by some bacteria. Fluoride forms fluorapatite which is less susceptible to damage caused by acid. Carious lesions and bulimia and enamel loss.
enamel derived from
epithelial tissue and is NOT replaced after formed
states of tooth development
bud, cap, bell appositional dentin and enamel, tooth eruption, and functional tooth
bud stage
- 20 buds formed
a. Invagination of oral epithelium into the mesenchyme. This process is induced by the neuroectodermal cells located in the mesenchyme.
b. Primordium of enamel lies within the invagination
c. On the mesenchymal side of the base of the invagination, mesenchymal cells form the primordium of the dental papilla
d. Cells of the epithelial tooth bud produce and secrete fibroblast growth factor-4 and bone morphogenetic proteins 2, 4, and 7. These substances regulate tooth shape.
cap stage
a. Inner enamel epithelium – cells will differentiate into ameloblasts
b. Dental papilla – neural crest cells of neuroectoderm will differentiate into odontoblasts while others will form the pulp
c. Early cap stage is induced by activin βA and bone morphogenetic protein 4 secreted by mesenchyme.
bell stage
- characterized by four layers that compose the enamel organ
a. Outer enamel epithelium
b. Inner enamel epithelium
c. Stratum intermedium – cells of this layer are attached via desmosomes to the non-secretory pole of the ameloblasts. Cells of the stratum intermedium elaborate and transport substances to the ameloblasts.
d. Stellate reticulum – stellate appearing cells in an ECM of glycosaminoglycans and water. Stellate cells are connected to one via desmosomes.
Amelogenesis
- process by which enamel is formed
a. Matrix production or secretory stage is carried out by secretory-stage ameloblasts. The partially mineralized enamel is elaborated directly on the surface of previously formed dentin. A Tome’s process is at the apical end of the ameloblast at this stage. Stratum intermedium is located at the base of the ameloblasts.
b. Matrix maturation is carried out by maturation-stage ameloblasts. Maturation involves removal of the organic components of partially mineralized enamel and the further mineralized of the enamel. Maturation-stage ameloblasts differentiate from secretory-stage ameloblasts. Many maturation-stage ameloblasts possess ruffled or striated borders, whereas others are smooth. A stratum intermedium is absent, instead a papillary layer is found at the basal domain of the ameloblasts.
tooth eruption
Ameloblasts degenerate following enamel maturation which occurs around the time of tooth eruption through the gingiva (gum).
Cementum
i. Mineralized (65%), bone-like substance that covers the dentin of the roots of teeth.
ii. Cementoblasts (derived from mesenchyme) actively secrete cementum and are located between the surface of cementum and the periodontal ligament; cementocytes and their processes are found in lacunae and canaliculi, respectively, along the lower root thereby forming cellular cementum.
- Acellular cementum is located more superiorly along the root.
iii. Unlike bone, cementum is avascular
iv. Collagen (type I) fibers run from the matrix of cementum to the bone of the tooth socket. These fibers are Sharpey’s fibers and are the principle component of the periodontal ligament.
Dentin
i. Mineralized tissue that lies deep to enamel and cementum; it is 70% inorganic. Organic component of dentin is similar to bone but includes two unique proteins that are necessary for mineralization: dentin phosphoprotein and dentin sialoprotein.
ii. Secreted by odontoblasts located on the inner surface of dentin (surface facing the pulp cavity). Odontoblasts are derived from neural crest cells of the adjacent mesenchyme.
iii. Elongated processes of the odontoblasts embedded in dentin form dentinal tubules. Exposure of dentinal tubules increases tooth sensitivity.
iv. Odontoblasts first secrete predentin which is unmineralized. Mineralization of the predentin forms dentin. Dentin is secreted throughout life.
Dental pulp and pulp cavity
i. Pulp cavity contains loose connective tissue well endowed with blood vessels and nerves.
ii. Nerves and blood vessels enter and leave through apical foramina of the roots.
iii. Pulp cavity becomes smaller with age as more dentin is secreted
Burtons line
blue gray gingival margin by teeth = LEAD POISONING
filiform
LACKS TASTE
epithelium derived from
oral epithelial which mature into enamel secretingcells = amelloblasts
odontoblasts
form dentin
from neural crest cells associated with neuro ectoderm of mesenchyme
dentin forms before or after enamel?
BEFORE.need surface for enamel
wall of the GI tube
mucosa
submucosa
muscularis externa (propria)
adventitia or serosa
mucosa of GI tube
1) Epithelium resting on a basal lamina
2) Lamina propria
a. Connective tissue
b. Glands
c. Blood vessels
d. Lymphatic tissue
e. Lymphatic vessel endowment – segmental differences exist
3) Muscularis mucosae
a. Two layers of smooth muscle (inner circular and outer longitudinal)
b. Contraction wrinkles the mucosa thereby increasing surface area. This facilitates absorption of nutrients and secretion.
submucosa of GI tube
i. Dense irregular connective tissue
ii. Glands are present in esophagus and duodenum
iii. Blood and lymphatic vessels
iv. Submucosal or Meissner’s plexus
muscularis externa (propria) of GI tube
i. Two layers of smooth muscle (inner circular and outer longitudinal)
ii. Contraction results in peristalsis
iii. Myenteric (Auerbach’s) plexus
Enteric nerve plexuses
A. Submucosal (Meissner’s) plexus
i. Parasympathetic postganglionic neurons and sympathetic postganglionic fibers
ii. Regulates glandular activity, blood flow, muscularis mucosae, and is sensory (mechano- and chemo-)
glands, wrinkles of muscle
B. Myenteric (Auerbach’s) plexus – located in muscularis externa
i. Parasympathetic postganglionic neurons and sympathetic postganglionic fibers
ii. Controls peristalsis–> main function
Esophagus layers
i. Mucosa
a. Stratified squamous, nonkeratinized epithelium
b. Cardiac esophageal glands found in lamina propria proximally and distally – secrete mucus for lubrication
c. Muscularis mucosae is better developed in the distal esophagus
ii. Submucosa – esophageal glands proper (seromucous) are found here
iii. Muscularis externa – upper 5% of esophagus = skeletal; upper esophagus = skeletal and smooth; and lower 50% or greater of esophagus = smooth
iv. Adventitia/serosa
a. Thoracic esophagus = adventitia
b. Abdominal esophagus = serosa
Barrett’s esophagus
i. Metaplastic columnar epithelium with goblet cells. PAS/ Alcian blue stains demonstrate acid (blue) and neutral mucins (reddish-purple). Goblet cells appear blue and mucous cells reddish/purple.
ii. Demarcation of stratified squamous and simple columnar epithelia
iii. At risk for progression to adenocarcinoma; clinical surveillance
Cancer staging (TNM) and lymphatic spread esophagus
i. Deeper invasion of cancer into wall leads to greater lymphatic exposure. This increases the prevalence of regional and distant lymph node metastases.
ii. As most lymphatic vessels are arranged longitudinally, cancer cells can spread cranially or caudally.
Achalasia - esophagus
i. Damage to certain neurons in the myenteric plexus causes constriction of the LES (sphincter into the stomach constricted)
ii. Distal constricted esophagus demonstrates a characteristic bird’s beak appearance
stomach regions
cardia, fundus, body, and pylorus
stomach rugae
i. Longitudinal folds in the undistended stomach
ii. Mucosa and submucosa form the folds
stomach layers
mucosa
submucosa
muscularis externa
mucosa of stomach
i. Surface epithelium - simple columnar, mucous cells
ii. Gastric pits are formed by the invagination of the surface epithelium into the lamina propria
iii. Glands empty into the gastric pits
iv. Gland regions: isthmus, neck, and fundus (base)
v. Lymphatic vessels (few in number) are confined deep in the lamina propria around the muscularis mucosae
muscularis externa of stomach
i. Inner oblique layer of smooth muscle – only present in certain regions of the stomach
ii. Middle circular layer of smooth muscle – thickened at the pylorus
iii. Outer longitudinal layer of smooth muscle
Fundus and body of stomach
a. Short gastric pits
b. Gastric glands (simple branched tubular) are long and harbor a diverse cell population
c. Glands divided into three regions: isthmus, neck, and fundus (base)
d. Isthmus region of gland
1. Surface epithelial cells - secrete mucus
2. Parietal (oxyntic) cells - secrete HCl and intrinsic factor in response to gastrin, histamine, and acetylcholine; mitochondria constitute 30-40% of total cell volume
3. Stem cells are located in this region intense proliferation
e. Neck region of the gland
1. mucous neck cells
2. many parietal cells (HCl and intrinsic factor; some chief cells (pepsinogen)**
3. Enteroendocrine cells (greater density in base, however)
f. Base region of the gland – also fundus
1. Contains many chief (zymogenic) cells – pepsinogen is secreted in response to acetylcholine
2. ** Enteroendocrine cells - hormone secreting cells. ***
3. Some mucous cells
4. Few parietal cells
Cardia of the stomach
a. Short gastric pits
b. Long glands in the lamina propria
c. Simple or branched tubular glands that coil as they approach the muscularis mucosae
d. Mucous cells
e. Few parietal cells
f. Few enteroendocrine cells
g. Stem cells
Pylorus of stomach
a. Deep gastric pits
b. Short glands
c. Branched tubular glands
d. Mucous cells
e. Enteroendocrine cells (ex., G cells secrete gastrin)
f. Few parietal cells
g. Stem cells
Gastric ulcers
i. Assault and defend
a. Mucosa is subjected to assault by pepsin and acid (pH 2.0)
b. Numerous defense mechamisms exists
1. Mucus and bicarbonate layer
2. Surface epithelial cells secreting mucus and bicarbonate, and other factors
3. Cell renewal
4. Alkaline tide-parietal cell level… H+ and bicarb by parietal cell –> floods into microcirculation
5. Microcirculation - mucous cells take it up too and secrete it with mucous
6. Sensory nerves
7. Prostaglandins
ii. Erosion (confined to mucosa) vs. ulcer (progressed into submucosa)
Gastroduodenal junction *****
pyloric sphincter is a thickening of the muscularis externa, chiefly its inner circular layer.****
small intestine structures that increase the surface area for absorption
i. Plicae circulares (valves of Kerckring) – permanent circular folds of submucosa and mucosa; increase surface 3-fold
ii. Intestinal villi - highly vascular processes of mucosa; increase surface aera 10-fold
iii. Microvilli - increase surface area 20-fold
iv. Gluten enteropathy (celiac sprue) – 4 signature histologic features
a. Enterocytes are disarrayed
b. Villus atrophy
c. Crypt (intestinal gland) hyperplasia
d. Inflammation of the lamina propria
layers of small intestine
mucosa
submucosa
muscularis externa
serosa
mucosa of small intestine
i. Epithelium
a. Rests on a basal lamina
b. Consists mainly of absorptive columnar cells with well-developed striated (brush) borders
c. ** Goblet cells – increase in number as the ileum is approached****
d. Intraepithelial lymphocytes (T cells)
ii. Lamina propria-leukocytes & lymphoctes (tcells)
a. Loose connective tissue that extends into the villi
b. Intestinal glands (crypts of Lieberkuhn)
c. Well endowed with blood and lymphatic vessels (lacteals)
d. Smooth muscle cells
e. Leukocytes and plasma cells
iii. Muscularis mucosae
submucosa of sm intestine
i. Moderately dense connective tissue
ii. Submucosal (Meissner’s) plexus
iii. Blood vessels
iv. Lymph vessels
Muscularis externa of sm intestine
i. inner circular layer of smooth muscle
ii. Outer longitudinal layer of smooth muscle
Intestinal glands (crypts of Lieberkuhn)
- small intestine
i. Lined by simple columnar epithelium resting on a basal lamina
ii. Openings of the glands are located between the villi
iii. Classified as simple tubular glands
iv. Cell types
a. Paneth cells – secrete lysozyme, defensins, and tumor necrosis factor-α. Paneth cells extend into right colon. - secrete into lumen
b. Enteroendocrine cells - secrete into vasculature - basal domain near lamina propria
c. Stem cells located toward base
Brunner’s (duodenal) glands
- small intestine
- a signature feature of the duodenum, secrete mucus and human epidermal growth factor. Well-developed proximally and less so distally.
- protection
jejunum vs ileum
j is thicker than i -
jejunum is more richly vascularized = red appearance in live person
Peyer’s patches and M cells
in ileum w/ villi—> antigen transportin cells
difference large intestine compared to small MUCOSA
a. No plicae circulares but do possess plicae semilunares (permanent folds of mucosa and submucosa)***
b. Absence of villi*
c. Intestinal glands are more numerous and longer*
d. Intestinal glands contain occasional Paneth cells in right-sided colon
e. Columnar cells have short, irregular microvilli: this presents an ill-defined striated (brush) border*
f. Goblet cells are more numerous in large intestine than small intestine. Goblet cell density increases distally.**
g. Lymphatic channels are poorly developed in the lamina propria. Lymphatic vessels are absent between the intestinal glands and are only found around the muscularis mucosae. This is clinically relevant in the case of an intramucosal carcinoma. Because of the paucity of lymphatic channels, the cancer has little or no potential to metastasize. Lymphatic channels extend radially rather than longitudinally.
difference large intestine compared to small MUSCULARIS EXTERNA
a. Outer longitudinal layer of smooth muscle does not completely surround the large intestine
b. Instead, three longitudinal bands of smooth muscle are found: these are the teniae coli.**
Vermiform appendix
- large intestines
i. lymphatic nodules are found in the lamina propria and submucosa
ii. Contains fewer and shorter intestinal glands
iii. Lacks teniae coli and villi
iv. Appendicitis
a. Fecalith
b. Mucous glands and pressure
c. Alterations in blood flow
d. Response of wall
e. Infection and mucosal ulceration
Rectum
i. Folds
a. Longitudinal folds (temporary) - folds of submucosa and mucosa
b. Plicae transversales recti (transverse rectal folds; aka valves of Houston) - folds of circular muscle of externa (some folds also have longitudinal muscle), submucosa, and mucosa
ii. Absence of teniae coli as they splay out and form a complete outer longitudinal layer to the muscularis externa. Important anatomic landmark to colorectal surgeons.
iii. Adventitia and serosa
iv. Solitary lymphatic nodules - no patches
Anal columns (columns of Morgagni)
longitudinal folds of submucosa and mucosa. Anal valves are located between distal adjacent anal columns with anal sinuses located lateral to the valves.
-separate anal canal from rectum
Pectinate (aka dentate) line to white line of Hilton
a. Stratified squamous, nonkeratinized epithelium
b. Stratified squamous, keratinized epithelium inferior to white line of Hilton - sebaceous glands are present
- forms a flap = anal valve.. space behind=anal sinus
Superior to pectinate line, submucosa contains (anal canal)
a large plexus of veins (internal hemorrhoids)
Inferior to pectinate line, lamina propria contains
a large plexus of veins (external hemorrhoids)
Anal cushions
(left lateral, right anterior, and right posterior) are composed of connective tissue, smooth muscle, and blood vessels. Function in anal continence.
Hemorrhoids
a. Internal – above dentate line – insensate to pain
b. External – below dentate line – sensate to pain
Outpocketings of the colonic wall are
false diverticula
true vs false diverticulum
A true diverticulum involves all wall layers; whereas, a false diverticulum only involves the mucosa and submucosa. Occur at points of wall weakness.
Colonic polyps
occur to robust proliferative activity of colonic crypt cells
Ulcerative colitis and lymphatic density
- inflammatory bowel
- Confined to the large intestine and perhaps the distal ileum
- Involves the mucosa and submucsa
Crohn’s disease
- inflammatory bowel disease
- Mouth to anus
- Involves all layers of the intestinal wall
- Fistula may form
Hirschsprung’s disease (congenital megacolon)
- Agangliosis of the myenteric and submucosal plexuses ABSENT
- Always involves the rectum and may also more proximal segments
- mega colon appearance from back up of poop
serosa vs adventitia
serposa inner ct with outer epithelial simple squamous lining (mesothelium) - slower spreading cancer
adventitia doesnt have mesothelium and has more CT - cancer spreads quicker here
4 histological features of gluten enteropathy
1) enterocytes are disarrayed
2) villus atrophy
3) crypt (intestinal gland) hyperplasia
4) inflammation of lamina propria
m cells
- microfold cell - immmune surveilance (APC)
- extends into lamina propria
appendix distingusih
mucosa = no villi submucosa = has lots of lymphatics
ilium distinguish
mucosa has vii
submucosa has lots of lymphatics
appendicitis
1) fecalith and intraluminal pressure - plug of poop that obstructs intestines–> anything below the plug is screwed and pressure on vasuclature to distal appendix=inflammatory process start
2) infection and mucosal ulceration
colonic diverticula
2 weaknesses- due to teniae ecolae
blood vessels in area make it worse
involve the mucosa and submucosa
not really in rectum bc muscle different
Glisson’s capsule
strong connective tissue capsule that covers the liver
Classic hepatic lobule and its blood supply
i. Stack of hexagonal plates of hepatocytes, sinusoids, and central vein (terminal hepatic venule)
ii. Portal canals are found at 3 to 6 angles of fathe liver lobule
a. Sparse, loose CT that is continuous with Glisson’s capsule
b. Portal triad = branches of hepatic artery, portal vein, and bile duct (IN PORTAL CANAL)
c. Lymphatic vessel and autonomic nerve fibers
d. Periportal space (space of Mall) is located between the connective tissue and adjacent haptocytes. Presumed to be the site of lymph origin
iii. Dual blood supply from portal vein (75%) and hepatic artery proper (25%)
iv. Sinusoids
a. Discontinuous endothelium with large fenestrations and discontinuous basal lamina
b. Kupffer cells (hepatic macrophages)
c. Perisinusoidal space (of Disse)
1. Hepatic stellate cell (aka perisinusoidal cell and cell of Ito) – contractile and CT elaboration=store LIPID - something to do with vit A but they are mostly inactive - if provoked not good
2. Microvilli of hepatocytes
iv. Terminal hepatic venule (aka central vein)
Kupffer cells
hepatic macrophages - remove RBC - bites out of RBC too.
Hepatic acinus (of Rappaport)
territory matching blood perfusion and metabolic activity 2 hepatocytes make up
Portal lobule
exocrine (bile) territory draining into bile duct - cetral vein to centarl vein x3 - 3 hepatocytes
Hepatic acinus zones
i. Zonation: Zones 1, 2, and 3 (div of labor b/w zones)
ii. Zonal response of cells in the three zones to nutrients, drugs, and toxic chemicals
a. Blood to zone 1
1. Increased oxygen
2. Decreased carbon dioxide
3. Decreased metabolic waste products
4. Increased nutrients
5. Bile stasis, iron toxicity and alfatoxin (perilobular damage)
6. Regenerative capacity
b. Blood to zone 3
1. Decreased oxygen
2. Increased carbon dioxide
3. Increased metabolic waste products
4. Decreased nutrients
5. First to show fat accumulation
6. More susceptible to damage (centrilobular)
a) Decreased nutrients, particularly during states of malnutrition
b) Ischemic/hypoxic damage
c) Several drug and toxic reactions (e.g., acetaminophen toxicity – CYP2E1 enzymes are localized in zone 3)
Hepatocyte structure
a. rER and sER
b. Mitochondria
c. Several small Golgi complexes
d. Peroxisomes
e. Glycogen and lipid deposits
f. Bile canaliculus
heptocyte functions
a. Detoxification via enzymes on SER
b. Glycogen metabolism SER
c. Blood protein synthesis and secretion RER
d. Bile acid synthesis and secretion SER
e. Bilirubin conjugation and secretion
1. Gilbert syndrome – bilirubin conjugation is reduced
2. Crigler-Najjar syndrome – bilirubin conjugation is reduced (type II) or absent (type I)
3. Dubin-Johnson syndrome – decreased secretion of conjugated bilirubin due to the absence of the mdr-2 canalicular transport protein
Fatty liver change and alcoholic cirrhosis
perisinusoidal cell (hepatic stellate cell) and its role in cirrhosis = fibrosis and contractility
cant process fatty acids so it accumulates
damage to zone 3 FIRST!
-cirrhosis is long term or due to hapattis - intense collagen accumulation that is walling off good cells - STLLATE CELLS are the culprits. it becomes proliferative and synthtic of ECM (collagen accumulation)
Hepatic ducts epithelium
Simple columnar epithelium
Biliary tract
A. Bile canaliculi
i. Limited by the plasma membranes of two hepatocytes
ii. Zonulae occludens
B. Canals of Hering – lined by (DUCTULAR CELLS) simple cuboidal cholangiocytes and hepatocytes; stem cell niche
C. Bile ducts (in portal triads) - Simple cuboidal to columnar epithelium - collect bile
-damage = alkaline phos accumulation
bile ducts epithelium type
Simple cuboidal to columnar epithelium
Hepatobiliary enzymes
they exist in the liver- dont need to know
gallbladder wall
i. Mucosa
a. Simple columnar epithelium, basal lamina
b. Lamina propria
c. Epithelium near the cystic duct forms tubuloacinar glands that secrete mucus for lubrication; glands increase with inflammation of the GB
d. No muscularis mucosae
e. Rokitansky-Aschoff sinuses may extend through muscularis
ii. Muscularis – smooth muscle cells have a random oblique orientation
iii. Connective tissue layer
a. Dense collaganeous CT with elastic fibers and adipose tissue
b. Blood vessels, lymphatics, and autonomic nerve fibers
c. Serous membrane (serosa) on its peritoneal surface and adventitia on its hepatic surface
invasion of GB cancer from gallbladder to the liver
- Absence of submucosa and serosa on the hepatic surface of the GB facilitates spread
- Presence of serosa on peritoneal surface of GB limits the spread of cancer to some extent.
Cholesterolosis
- Benign condition
- Macrophages laden with cholesterol = foam cells
type of glad pancreas
exocrine= compound acinar
endocrine=pancreatic islets of langerhans
Acinar cells
i. Base of cell
a. Rests on basal lamina
b. Basophilic cytoplasm
c. Extensive RER is present
d. Nucleus is located towards the base
ii. Apical region
a. Acidophilic cytoplasm
b. Presence of zymogen granules
c. Secretion of proenzymes and enzymes
Centroacinar cells
i. Their nuclei project into the centers of acini
ii. Form the intra-acinar portion of the intercalated duct
iii. This arrangement is unique to the pancreas
Pancreatic duct cells secrete:
Importance?
water, ions of which HCO3- is important to neutralize the acidic chyme
liver framework made up of
type III reticular collagen
Gilbert syndrome –
bilirubin conjugation is reduced BENIGN
Crigler-Najjar syndrome –
bilirubin conjugation is reduced (type II) or absent (type I)
Dubin-Johnson syndrome –
decreased secretion of conjugated bilirubin due to the absence of the mdr-2 canalicular transport protein
-
respiratory bronchiole –> alveolar ducts and alveoli
