2025 Anatomy Exam 3 Flashcards
Lectures 9-12: Urinary Tract
The Urinary System
The Urinary System Parts
The urinary system consists of:
Kidneys—produce urine
And the associated nephrons
Produce urine
Urinary tract—transports/stores urine
Ureters
Urinary bladder
Urethra
Urine is stored in the bladder until it is eliminated (micturition/urination)
The Kidneys
The right kidney
Anterior surface covered by the liver, right colic flexure, and duodenum
The left kidney
Anterior surface covered by the spleen, stomach, pancreas, left colic flexure, and jejunum
Positioned slightly higher than right kidney
An adrenal gland is located on the superior surface of each kidney
The kidneys are retroperitoneal
Three Layers of Kidneys
There are three layers of connective tissue that function to protect the kidneys:
Fibrous capsule
Perinephric fat (perirenal fat capsule)
Renal fascia
Connective Tissue Layers of Kidney
Superficial Anatomy of the Kidney
A typical kidney
Size
10 cm long (4 inches)
5.5 cm wide (2.2 inches)
3 cm thick (1.2 inches)
Sectional view
The medial indentation is the hilum
Renal arteries enter at the hilum
Renal veins and ureters exit at the hilum
Sectional Anatomy of the Kidney
Consists of:
Renal cortex
Renal medulla, deep to the cortex, consisting of:
Renal pyramids
Renal papillae
Renal columns
A kidney lobe consists of a renal pyramid, overlying renal cortex, and adjacent renal columns
Renal pelvis (comprises most of the renal sinus) consists of:
Minor calyx
Major calyx
Calyces of Kidney
Blood Supply of Kidneys
The Blood Supply to the Kidneys
Beginning with blood in the renal arteries, blood flows to:
Afferent arterioles
Glomerular capillaries
25% of the cardiac output goes to the kidneys
Circulation in the Renal Cortex
Flow of Blood
After filtration occurs in the nephrons, blood leaves the kidneys via the following vessels:
Glomerular capillaries
Efferent arteriole
Peritubular capillaries
Cortical radiate veins
Arcuate veins
Interlobar veins
Renal vein
There are no segmental veins
*** We are worried about the Nephrons
Innervation of the Kidneys
Receives sympathetic nerve fibers from the celiac and inferior mesenteric ganglia via renal nerves
Neural innervation serves to:
Regulate renal blood flow and pressure
Stimulate renin release
Stimulate water and sodium ion reabsorption
The Nephron
Histology of the Kidney
The Nephron and Collecting System
Each nephron consists of a renal corpuscle and a renal tubule
Renal corpuscle consists of glomerular capillaries (glomerulus) and glomerular capsule
Glomerular filtrate leaves the glomerular capillaries and enters glomerular capsule
Afferent arteriole and efferent arteriole form the vascular pole
Renal tubule
Proximal convoluted tubule (PCT)
Nephron loop
Distal convoluted tubule (DCT)
Filtrate from the DCT empties into the collecting system
Connecting tubules from several nephrons lead to a common collecting duct
The collecting duct passes through the renal pyramids
Filtrate in the collecting duct then enters the:
Papillary duct → minor calyx → major calyx
Filtrate is now called urine
Urine leaves the kidneys via the urinary tract:
Renal Pelvis to the Ureter → urinary bladder → urethra
Two Main Types of Nephrons
Two main types of nephrons
Cortical nephrons
85 percent of the nephrons are cortical
Most of the nephron is located in the cortex
Have a relatively short nephron loop
Juxtamedullary nephrons
15 percent of the nephrons are juxtamedullary
Capsule is located near the border of the cortex and the medulla
Have a long nephron loop
Functions of the Nephrons
The Nephron and Collecting System
Main functions of the nephron
Reabsorbs useful organic material and ions from the filtrate
Reabsorbs more than 99 percent of the water from the filtrate
Enhances the elimination of wastes by actively secreting them into the filtrate
Parts of Renal Corpuscle
The Renal Corpuscle
Consists of:
Glomerular capsule (Bowman’s capsule)
Glomerular capillaries (glomerulus)
Glomerular capsule consists of:
Capsular outer layer (parietal layer)
Made of squamous cells that are continuous with the lining of the PCT
Folds back to form the visceral layer
Visceral layer
Makes up the epithelial lining of the glomerular capillaries
Renal Corpuscle
The Renal Corpuscle
Filtration within the renal corpuscle involves five filtration barriers
Endothelial surface layer
Glomerular capillary endothelium
Basement membrane
Glomerular epithelium
Subpodocyte space
Filtration within the renal corpuscle
Endothelial surface area
Luminal surface of capillary endothelium has a thick meshwork
Limits filtration of large plasma proteins
Glomerular capillary endothelium
The glomerular capillaries are fenestrated
Have openings 0.06–0.1 microns
Too small for blood to pass through (RBC = 7 microns)
Basement membrane
Encircles the capillary endothelium of two or more capillaries
This dense layer restricts the passage of large proteins but permits smaller proteins
Permits the passage of ions and nutrients
Mesangial cells provide support for capillaries and regulate blood flow and filtration
Glomerular epithelium
Consists of special cells called podocytes
Podocytes have long cellular extensions (secondary processes) that wrap around the basal lamina
These extensions have gaps called filtration slits
Subpodocyte space
Comprises most of the filtration space of the glomerulus
Assists the filtration slits of podocytes
Filtrate passing these barriers consists of water, ions, and small organic molecules (glucose, fatty acids, amino acids, and vitamins)
Filtrate passing through contains very few plasma proteins
Many substances are subsequently reabsorbed in the nephron tubule
The Proximal Convoluted Tubule
Begins at tubular pole of the renal corpuscle
Lined with simple cuboidal epithelium containing microvilli
Reabsorbs:
Organic nutrients
Plasma protein
60 percent of the sodium and chloride ions and water
Other ions (for example, calcium, potassium, phosphate, and bicarbonate)
The Nephron Loop (Loop of Henley)
Descending limb
Water leaves this portion and enters the bloodstream (thereby preventing dehydration)
Ascending limb
Pumps ions (sodium ions and chloride ions) out of the tubular fluid
Impermeable to water
Both loops comprised of simple squamous epithelium
The capillaries surrounding the nephron loop are called the vasa recta
The Distal Convoluted Tubule
Active, regulated secretion of ions and acids
Selective reabsorption of sodium and calcium ions
Reabsorption of water
The Juxtaglomerular Complex
Located in the region of the vascular pole
Consists of:
Macula densa cells
Juxtaglomerular cells
Extraglomerular mesangial cells
Produces two hormones
Renin: involved in regulating blood pressure
Erythropoietin: involved in erythrocyte production
The Collecting System
of Kidneys
Consists of:
Connecting tubules
Collecting ducts
Papillary ducts
The DCT of each nephron connects to a connecting tubule
Several connecting tubules drain into a collecting duct
The cells of the collecting ducts make final adjustments to the concentration of the urine that is about to exit the kidneys
Several collecting ducts converge and empty into a papillary duct
Papillary ducts empty into minor calyxes
At this point the filtrate is no longer modified and is properly called urine
Epithelium of collecting system
Begins as simple cuboidal in collecting tubules
Transitions to simple columnar in collecting and papillary ducts
Urine moves from minor calyx to major calyx
Then drains to renal pelvis
Then drains to ureters
Transitional epithelium lines the minor and major calyces and renal pelvis
The Ureters
Exit the kidney at the hilum area
Extend to the urinary bladder
Enter the urinary bladder on the posterior/inferior side
The ureteral orifices enter the urinary bladder in the trigone area
Peristaltic contractions and gravity move urine toward the urinary bladder
Histology of the Ureters
Each ureter consists of three layers
Inner mucosa
Lined with transitional epithelium
Middle muscular layer
Consisting of longitudinal and circular smooth muscles
Adventitia
This is continuous with the fibrous capsule and parietal peritoneum
The Urinary Bladder Male
Males
The base of the urinary bladder is between the rectum and the symphysis pubis
The Urinary Bladder Male (Lateral View)
The Urinary Bladder Female (Lateral View)
Females
The base of the urinary bladder is inferior to the uterus and anterior to the vagina
Histology of the Urinary Bladder
Mucosa
Has folds called rugae to increase bladder volume
Lined by transitional epithelium
Trigone region funnels urine to the urethra
The smooth muscle layer of the urinary bladder is called the detrusor
The neck of the urinary bladder surrounds the entrance to the urethra
Lined with a smooth muscle that makes up the internal urethral sphincter
This is under involuntary control
The Urethra
Female
3 to 5 cm in length
The external urethral orifice is near the anterior wall of the vagina
Transitional epithelium only at neck of the urinary bladder, remainder is stratified squamous
Male
18 to 20 cm in length
Subdivided to form the prostatic urethra, membranous urethra, and spongy urethra
Complex histology
Transitional epithelium near bladder
Changes to pseudostratified columnar then stratified columnar
Finally, stratified squamous near external urethral opening
Prostatic urethra
Passes through the prostate gland
Membranous urethra
Short segment that penetrates the muscular wall of the pelvic cavity in the inguinal region
Spongy urethra (penile urethra)
Extends through the penis to the external urethral orifice
As the urethra passes through there is a skeletal muscle that makes up the external urethral sphincter
This is under voluntary control—this is the sphincter we learned to control as an infant
We lose control as we age
We lose control due to some spinal cord injuries
Skeletal System Introduction
Structure of Bone
The Histological Organization of Mature Bone
Collagen gives tensile strength
The Cells of Mature Bone
Osteocytes
Mature bone cells
Maintain the protein and mineral content of the matrix
Osteoblasts
Immature bone cells
Build the Matrix
Osteoblasts convert to osteocytes
Secrete osteoid, an unmineralized protein matrix that helps form bone tissue.
Osteoprogenitor cells
Found on the inner and outer surfaces of bones
Differentiate to form new osteoblasts
Osteoclasts
Secrete acids, which dissolve the bones
Active when we need Calcium… receive PTHormone and start to dissolve the matrix
Bone Cells
The Osteon
It is the basic unit of skeletal bones
Consists of:
Central canal (Haversian canal) – Vascular and nerve supply of the osteon
Canaliculi – Processes of the osteocyte. Serves for the passage of substances between the osteocytes and blood vessels
Lacunae – Osteocytes contained within
Lamellae – Bone matrix (the rings of the bone)
Histological Structure of a Typical Bone
Single Osteon
Two types of osseous tissue
Compact bone (dense bone)
Compact bones are dense and solid
Forms the walls of bone outlining the medullary cavity
Medullary cavity consists of bone marrow
Spongy bone (trabecular bone)
Open network of plates
Concentric lamellea = matrix
Spongy Bone
Structural Differences of Two Bone Types
Compact bone
Consists of osteons
Makes up the dense, solid portion of bone
Spongy bone
Trabeculae are arranged in parallel struts
Trabeculae form branching plates
Trabeculae form an open network
Creates the lightweight nature of bones
Functional Differences of Two Types of Bone Types
Compact bone
Conducts stress from one area of the body to another area of the body
Generates tremendous strength from end to end
Weak strength when stress is applied to the side
Spongy bone
Trabeculae create strength to deal with stress from the side
Bone Parts (1)
Red Marrow gets replaced as we get older with Yellow Marrow (fat)
Bone Parts (2)
Epiphysis of Bone
Organization of Compact and Spongy Bone
Epiphysis
Each end of the long bones
Diaphysis
Shaft of the long bones
Metaphysis
Narrow growth zone between the epiphysis and the diaphysis
Disappears as we become adults
The Periosteum
Periosteum
Outer surface of the bone
Isolates and protects the bone from surrounding tissue
Provides a route and a place for attachment for circulatory and nervous supply
Senses pain
Attaches the bone to the connective tissue network of the deep fascia
Periosteum and Tendons
Tendons are cemented into the lamellae by osteoblasts
Therefore, tendons are actually a part of the bone
Tendon grows into blood
Enthesis = where bone and tendon meet
Endosteum
Inner surface of bone
Lines the medullary cavity
Consists of osteoprogenitor cells
Anatomy and Histology of the Periosteum and Endosteum
Bone Development and Growth
The Epiphyseal plate aka the “growth plate”
Area of cartilage in the metaphysis
Also called the epiphyseal cartilage
Cartilage near the diaphysis is converted to bone
The width of this zone gets narrower as we age
Circulatory Supply to a Mature Bone
Factors Regulating Bone Growth
Nutrition
Calcium ions
Phosphate ions (inverse relationship with calcium)
Magnesium ions (parallel relationship with calcium)
Citrate
Carbonate ions
Sodium ions
Vitamins A, C, D (calcitriol)
Exercise
18-19 years old bone growth is essentially over
Excess Growth hormone before puberty = gigantism
Excess Growth hormone after puberty = acromegaly (but doesn’t lengthening the bones because plates already closed)
Categories of Bones
There are seven broad categories of bones according to their shapes:
Sutural bones
Irregular bones
Short bones
Pneumatized bones
Flat bones
Long bones
Sesamoid bones
Bone Markings Include
Projections
Tuberosities, trochanters, tubercle, trochlea
Depressions
Grooves, sulci (e.g. sulcus tali), fossa,
Fissures – deeper sulci or canyon like
Foramina (hole)
Canals (meatuses)
Muscle Introduction
Skeletal = Striated = Voluntary
Visceral = Smooth = Involuntary
Cardiac = Have Striations = Involuntary
Muscle Tissue Four Basic Properties
Anatomy of Skeletal Muscles
Gross anatomy is the study of:
Overall organization of muscles
Connective tissue associated with muscles
Nerves associated with muscles
Blood vessels associated with muscles
Microscopic anatomy is the study of:
Myofibrils
Myofilaments
Sarcomeres
Gross Anatomy of Muscle
Connective tissue of muscle:
Epimysium: dense tissue that surrounds the entire muscle
Perimysium: dense tissue that divides the muscle into parallel compartments of fascicles
Endomysium: dense tissue that surrounds individual muscle fibers
Tendons and Aponeuroses:
Epimysium, perimysium, and endomysium converge to form tendons
Tendons connect a muscle to a bone
Aponeuroses connect a muscle to a muscle
Nerves and blood vessels:
Nerves innervate the muscle
There is a chemical communication between a nerve and a muscle
The nerve is “connected” to the muscle via the motor end plate
This is the neuromuscular junction
Blood vessels innervate the endomysium of the muscle
They then branch to form coiled networks to accommodate flexion and extension of the muscle
Neuromuscular Junction (1)
Neuromuscular Junction Actual
Motor End Plate
Axon Terminal and Muscle Fiber do not touch = neuromuscular junction
Has Sodium Channels in it on the muscle side, which leads to depolarization
Microanatomy of skeletal muscle fibers
Sarcolemma
Membrane that surrounds the muscle cell
Sarcoplasm
The cytosol of the muscle cell
Muscle fiber (same thing as a muscle cell)
Can be 30–40 cm in length
Multinucleated (each muscle cell has hundreds of nuclei)
Nuclei are located just deep to the sarcolemma
Storage in Muscle:
Glucose = Glycogen
Hemoglobin = Myoglobin
The Formation and Structure of a Skeletal Muscle Fiber
Myofibrils and Myofilaments
The sarcoplasm contains myofibrils:
Myofibrils are responsible for the contraction of muscles
Myofibrils are attached to the sarcolemma at each end of the muscle cell
Surrounding each myofibril is the sarcoplasmic reticulum
Myofibrils are made of myofilaments:
Actin
Myosin
Sarcomere Structure
Sarcomere Organization
Myosin (thick filament)
Actin (thin filament)
Both are arranged in repeating units called sarcomeres
All the myofilaments are arranged parallel to the long axis of the cell
Sarcomere
Main functioning unit of muscle fibers
Approximately 10,000 per myofibril
Consists of overlapping actin and myosin
This overlapping creates the striations that give the skeletal muscle its identifiable characteristic
Each sarcomere consists of:
Z line (Z disc)
I band
A band (overlapping A bands create striations)
H band
M line
Levels of Organization of Muscle
Skeletal muscles consist of muscle fascicles
Muscle fascicles consist of muscle fibers
Muscle fibers consist of myofibrils
Myofibrils consist of sarcomeres
Sarcomeres consist of myofilaments
Myofilaments are made of actin and myosin
Actin
Twisted filament consisting of G actin molecules
Each G actin molecule has an active site (binding site)
Myosin cross-bridges bind to the active sites on actin
Tropomyosin: A protein that covers the binding sites when the muscle is relaxed
Troponin: Holds tropomyosin in position
Motor Units and Muscle Control
Motor Units (motor neurons controlling muscle fibers)
Precise control
A motor neuron controlling two or three muscle fibers
Example: the control over the eye muscles
Less precise control
A motor neuron controlling perhaps 2000 muscle fibers
Example: the control over the leg muscles
The Number is the number of fibers one nerve goes to
Muscles can be classified based on shape or by the arrangement of the fibers
Parallel muscle fibers
Convergent muscle fibers
Pennate muscle fibers:
Unipennate muscle fibers
Bipennate muscle fibers
Multipennate muscle fibers
Circular muscle fibers
Parallel muscle fibers
Muscle fascicles are parallel to the longitudinal axis
Examples: biceps brachii and rectus abdominis
Convergent muscle fibers
Muscle fibers form a broad area but come together at a common point
Example: pectoralis major
Pennate muscle fibers: Unipennate
Muscle fibers form an oblique angle to the tendon of the muscle
An example is unipennate
All the muscle fibers are on the same side of the tendon
Example: extensor digitorum
Pennate muscle fibers: Bipennate
Muscle fibers form an oblique angle to the tendon of the muscle
An example is bipennate
Muscle fibers are on both sides of the tendon
Example: rectus femoris
Pennate muscle fibers: Multipennate
Muscle fibers form an oblique angle to the tendon of the muscle
An example is multipennate
The tendon branches within the muscle
Example: deltoid muscle
Circular muscle fibers
Muscle fibers form concentric rings
Also known as sphincter muscles
Examples: orbicularis oris and orbicularis oculi
Origin, Insertion, and Action
Origin
Point of muscle attachment that remains stationary
Insertion
Point of muscle attachment that is movable
Action
The function of the muscle upon contraction
Two methods of describing muscle actions
The first makes reference to the bone region the muscle is associated with
The biceps brachii muscle causes “flexion of the forearm”
The second makes reference to a specific joint the muscle is associated with
The biceps brachii muscle causes “flexion at the elbow”
Muscle Terminology (1)
Prime movers example:
Biceps brachii – flexes the lower arm
Antagonists example:
Triceps brachii – extends the lower arm
Synergists example:
Latissimus dorsi and teres major – contract to move the arm medially over the posterior body
Fixators example:
Flexor and extensor muscles contract at the same time to stabilize an outstretched hand
Muscle Terminology (2)
Muscle Terminology (2)
Muscle Terminology (3)
