HISTO LAB

• Urethra


  Fibromuscular tube that conveys urine from the urinary bladder to the exterior through the external urethral orifice
• Urethra


  • Size, structure, and functions differ in males and females
  • In females, the urethra is solely a urinary duct
  • In males, it also serves as a pathway for the ejaculation of sperm
• Components of the urinary system

  • Pelvicalyceal system
  • Ureter
  • Bladder
  • Urethra
• Pelvicalyceal system


  Conveys urine from the tips of the renal papillae into the ureter
• Ureter


  Carries urine to the bladder
• Ureter


  • Smooth muscle, no distinct layer structure
  • 3 muscle layers: inner spiral (longitudinal), outer spiral (circular layers)
  • Transitional epithelium (urothelium)
• Bladder


  Distensible reservoir for urine
• Bladder


  • Located in the pelvis, posterior to the pubic symphysis
  • Its size and shape changes as it fills
  • Contains 3 openings: 2 ureteric orifices, 1 internal urethral orifice
• When the bladder is distended, the openings of the ureters are compressed, reducing the possibility of the reflux of urine into the ureters
• Contraction of the smooth muscle of the bladder wall compresses the openings of the ureters into the bladder, helping prevent the spread of infection from the bladder and urethra
• Ureter


  Conducts urine from the renal pelvis to the urinary bladder
• Ureter


  • Approximate length: 24-34cm
  • Smooth muscle is arranged in layers: inner longitudinal, middle circular, outer longitudinal
  • Outer longitudinal layer is present at the distal end, particularly in the portion of the ureter that passes through the bladder wall, and continues into the wall of the bladder
• Main roles of the nephron


  • Reabsorption of Na
  • Reabsorption of 75% of the glomerular filtrate
  • Establish countercurrent medullary concentration gradient via countercurrent multiplication
  • Secretion of H and K
• Renal corpuscle


  Filters the blood plasma, represents the beginning of the nephron
• Renal corpuscle


  • Spherical and has an average diameter of 200 micrometers
  • Contains the filtration apparatus: glomerular endothelium, underlying basement membrane, visceral layer of Bowman's capsule
• Nephron


  Fundamental structural and functional unit of the kidney, responsible for the production of urine
• Nephron


  • 85% Cortical Nephrons, 15% Juxtamedullary Nephrons
  • Collecting ducts are responsible for the final concentration of the urine
• Parts of the kidney


  • Kidney lobes
  • Renal pyramid
  • Cortex and medulla
  • Renal capsule
  • Renal sinus
• Kidney lobes


  Each human kidney contains 8 to 18 lobes, can be unilobular or multilobular
• Renal pyramid


  Conical structures in the medulla, containing the tubules and vasculature for urine concentration
• Renal pyramid


  • Usually 8 to 12, but as many as 18 may be present in the human kidney
  • Bases face the cortex, apices face the renal sinus
  • Divided into outer medulla and inner medulla
• Renal cortex and medulla

  Two distinct regions of the kidney, cortex is the outer reddish-brown part, medulla is the much lighter-colored inner part
• Renal cortex and medulla

  • Cortex contains 90-95% of the blood, medulla contains 5-10%
• Renal capsule


  Connective tissue covering the kidney surface, consisting of an outer layer of fibroblasts and collagen fibers, and an inner layer of myofibroblasts
• Renal sinus


  Loose connective tissue and a flat filled space that surrounds the renal vein, renal artery and pelvis
• Functions of the kidneys

  • Vascular tone regulation
  • Erythropoiesis
  • Calcium homeostasis
  • Excretion
  • Reabsorption
  • Acid-base homeostasis
  • Water and sodium metabolism
• Kidneys are large, reddish, bean-shaped, retroperitoneal organs located on each side of the vertebral column
• Kidneys


  • Covered by a fibrous capsule, perirenal fat, renal fascia, and extensive pararenal fat
  • Extend from 12th thoracic to the 3rd lower vertebrae
  • Right kidney positioned slightly lower
  • Each measure approximately 10 cm long x 6.5 cm wide x 3 cm thick, and weigh about 150 g
• Functions of the kidneys

  • Filtration of small molecules from blood plasma to form a filtrate
  • Selective reabsorption of most of the water and other molecules from the filtrate, leaving behind excess and waste materials to be excreted
• Digestive System


  • Oral Cavity
  • Lip
  • Gingiva (gum)
  • Teeth
  • Hard palate
  • Soft palate
  • Retromolar trigone
  • Tongue
  • Uvula
  • Tonsil
  • Buccal mucosa
  • Floor of mouth
• Lips


  • Central core of striated or skeletal muscle
  • Embedded in elastic fibroconnective tissue
  • Skeletal muscle: Orbicularis Oris
  • Externally covered by skin, hair follicles, sebaceous glands, sweat glands
• Vestibule


  Space between the lips and cheeks and outer aspect of the gums and teeth
• Gingiva


  • Thick Stratified Squamous Epithelium
  • Dense Connective Tissue
  • Fixed to the bone
  • Covers hard palate
  • Greater thickness
  • Firmer attachment
  • Greater degree of keratinization
  • More resistant to attrition when chewing
• Mucus Membrane


  • Non-Keratinized: Floor of the Mouth, Lower surface of the tongue, Inside the lips, Cheeks
  • Keratinized: Hard Palate, Gingiva, Dorsal surface of the tongue, Tonsils, Soft Palate
• Layers of the Mucous Membrane

  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum corneum
• Tongue


  • Stratified Squamous Epithelium
  • Consists of interlacing bundles of striated muscle
  • Oriented vertically, horizontally, longitudinally, and intersecting at right angles
  • Undersurface: Non keratinized
  • Dorsal portion: Covered by relatively thick epithelium, Firmly bound to connective tissue, Keratinized or incomplete keratinized, Covered by lingual papillae
• Taste Buds


  • 3,000 in the human tongue
  • Pale ovoid bodies, 50-80 um x 30-50 um
  • Consists of 50 to 90 fusiform cells, Wider at the base than the apex
  • Have sensory nerve fibers
• Salivary Glands


  • Minor Glands: Small aggregates of salivary gland, Short branching tubules lined with mucous cells
  • Major Glands: Parotid Gland, Submandibular Gland, Sublingual Gland
• Salivary Glands


  • Usually in pairs
  • Situated at some distance from oral epithelium
  • Acini: Mucous cells, Serous cells, Seromucous acini
• Mucous Acini


  • Lumen is larger than serous acini
  • Single layer of plump pyramidal cells
  • Cytoplasm filled with mucigen (antecedent or mucus)