Structures and anatomy Flashcards
Simple squamous epithelium
Single layer of flat cells - found in absorptive/filtrative tissues, e.g. blood vessel endothelia, mesothelia lining all body cavities (peritoneum, pericardium, pleura)
Simple cuboidal epithelium
Single layer of cube-shaped cells - found in glands and ducts, e.g. thyroid (secreting thyroglobulin-containing colloid), walls of kidney tubules, ducts in breast lobules, cervix
Simple columnar epithelium
Single layer of columnar cells, often including Goblet cells - lines the digestive tract
Pseudostratified epithelium
One layer of cells, but different shapes and sizes give layered appearance, pseudostratified columnar (cilliated) epithelia found in nasal passage (URT), trachea, bronchi (LRT), inner ear, vas deferens, prostate, epididymis
Stratified squamous epithelium
Found (for example) in rectum, vulva, pharynx, and conjuctiva, layers of flat cells
Transitional epithelium
Changes shape when stretched (transitional relaxed/distended epithelium) - urethra, bladder, ureter
Stratified cuboidal epithelium
Found in sweatgland ducts and male urethra
Layers of skin
Epidermis - stratum corneum, lucidum, granulosum, spinosum, basale
Dermis - papillary, reticular
Hypodermis
Basal lamina protein network
Composed of type IV collagen, laminin, entactin & perlecan so cells cannot pass through - blood supply to epithelia is via diffusion from capillaries in connective tissue underlying basement membrane (basal lamina + lamina reticularis)
Upper GI includes…
Oesophagus, stomach, duodenum
Lower GI includes…
Jejunum, Illeum (SI) and colon, AKA the large bowel/LI
Large intestine - proximal to distal
Caecum -> Ascending colon -> Transverse colon -> Descending colon -> Sigmoid -> Rectum
Layers of digestive system epithelia - outside to inside
Serosa (below diaphragm), or adventitia (above diaphragm) -> Longitudinal muscle -> Circular muscle -> Submucosa -> Muscularis mucosa -> Mucosa
Peyer’s patches
A group of well-organized lymphoid follicles located in the lamina propria and submucosa of the distal SI(ileum, jejunum and sometimes duodenum) - almost 50% are in the distal ileum; control gut flora and provide immune defense
Brunner’s glands
Secrete alkaline mucus to protect duodenal lining from stomach acid
Duodenum - unique features/findings
Leaflike villi, crypts of Lieberkuhn, Brunner’s glands in submucosa
Jejunum - unique features/findings
Finger-like villi, well-developed picae circulares, crypts of Lieberkuhn but no glands in submucosa
Illeum - unique features/findings
Shorter villi, M cells, Peyer’s patches through lamina propria and submucosa
Villus lumen contains…
Capillary villus plexus, and a lacteal (lyphatic vessel for lipid drainage)
Oesophagus structure
Outer longitudinal muscle, inner circular muscle, then submucosa (with submucosal glands and plexi), muscularis mucosa, and mucosa - wherein mucosal folds are lined by stratified squamous epithelium; muscle is striated/skeletal at upper (pharyngeal) end, then get progressively more smooth-muscle-based
Stomach - two sections
Orad area - Fundus and (proximal) part of body - It and the lower oesophageal sphicter relax during swallowing
Caudad area - Distal body and atria - Controls gastric emptying rate
Gastric glands - structure and cell types
2+ long, straight tubular glands (ending at the muscularis mucosae) join and open into one pit through a narrow neck
Pit - Simple columnar epithelium, surface mucous cells (non-Goblet - oval nucleus instead of flat, lots of small mucous droplets)
Mucous neck cells in narrow ‘isthmus’
Parietal cells & chief cells
Parietal and chief cells in gastric pits
Parietal cells - In upper body of gastric gland, separated by clusters of chief cells, secrete HCl
Chief cells - In lower gastric gland, basal domain is basophilic, apical domain has secretory granules to secrete pepsinogen
Connective tissue - types of fibers and staining
Collagen - thick pink, elastic - purple/black, reticular - fine black
Adipose connective tissue location and appearance
Throughout body - Single nucleus around lipid droplet
Areolar connective tissue location and appearance
Under epithelia, like in digestive tract/respiratory system - Looks like neurons, loose fibers in all directions, fibroblasts interspersed
Reticular connective tissue location and appearance
In lymph nodes, Peyer’s patches, bone marrow, kidney, liver, spleen - Needs special stain, thicker black fibers, more meshed as opposed to long straight lines (areolar), circular cells in lymph nodes
Dense regular connective tissue location and appearance
Tendons, ligaments, aponeuroses, resp. tract - Large bundles of collagen fibers running in one direction, fibroblasts sandwiched inbetween
Dense irregular connective tissue location and appearance
Dermis and liver/spleen capsules - Large bundles of parallel collagen fibers, but bundles run in different directions
Elastic connective tissue location and appearance
Mainly arteries - Squiggly zig-zags of elastic fibres
Elastic cartilage location and appearance
External ears, eustachian tubes, larynx - Continous line of lacunae arranged next to each other, several layers, dark staining elastic fibres around the lacunae
Fibrocartilage location and appearance
Inter-vertebral discs, intra-articular cartilage of knee/wrist/TMJ joints - Fibres in-between but lacunae are separated, arranged in different areas/segments
Hyaline cartilage location and appearance
Ribs, nose, larynx, trachea - Small bunches of lacunae dispersed evenly throughout the tissue, light/glassy staining around them with no fibres
Alveoli structure
Terminal bronchioles -> Respiratory bronchioles -> Alveolar ducts -> Alveolar sacs
Surface epithelium - 40% Type I pneumocytes - Simple squamous epithelium, barrier
60% Type II pneumocytes - Larger, rounder cells with more cytoplasm, secrete surfactant
+ Supporting tissue
+ Blood vessels
Epithelia in bronchi/bronchioles vs. alveoli, and glands
Walls of bronchi and bronchioles are ciliated cuboidal epithelial cells
Seromucinous glands exist under bronchal epithelia
Bronchioles have no goblet cells, no SM glands, and no cartilage
Alveoli are squamous epithelial
Liver - general structure
L/R Hepatic duct, common hepatic duct, gallbladder joins, cystic duct, common bile duct, pancreas, pancreatic duct, duodenum, sphincter of Oddi
Hepatic triad
Hepatic triads - Portal vein, hepatic artery, bile duct (+ also a lymphatic vessel but not included in triad)
Liver - lobule/sinusoid structure
Lobule - Central vein + Acinus
Acinus - Sinusoids lined by hepatocytes, Kupffer cells, hepatic artery branch, hepatic portal vein branch, bile duct, bile canaliculi
Sinusoid - Lumen + Kupffer cells, fenestrated endothelial cells, space of disse
Space of disse - Stellate and dendritic cells
Then hepatocytes lining outside of sinusoid, with bile canaliculi interspersed
https://imgur.com/a/o8jZhE6
Bile secretion
Produced by hepatocytes, modified by cholangiocytes lining bile ducts, transported into gallbladder for storage
CCK -> Gallbladder contraction, pushing bile through common bile duct
Sphincter of Oddi also relaxes -> Bile enters duodenal lumen
Secretin also participates in bile flow into SI, stimulating biliary and pancreatic ductular cells to secrete bicarbonate and water in response to the presence of acid in the duodenum
Bile function
Lipid absorption - Emulsifies fats, breaking down large lipid droplets into smaller ones, because bile salts are amphipathic (hydrophilic and -phobic ends)
Waste elimination - Excess cholesterol is converted into bile acids, excreted through biliary system via stool
Liver - Lobule vs Acinus
The lobule is a hexagonal structure composed of a central portal, with the … supplying it at the corners. In contrast, the acini divide the lobule into triangular sections, with the portal vein at the apex and the … on the base.
TDLU basic structure (and IHC)
The TDLU is lined by a double layer of cells; an inner epithelial luminal layer and an outer layer of specialized myoepithelial cells that sit on the basement membrane. This outer basal layer stains brown with CK14 IHC in normal breast, not the inside. The TDLU is surrounded by collagen, adipose tissue, and interspersed connective cells - forming the background stroma. CD44 can also stain rare but vital breast stem cells within this double-walled structure.
