ANA 204 GIT & Urinary System Flashcards
Describe the two divisions of the digestive system
Digestive system can be divided into two components
UPPER DIGESTIVE SEGMENT
* Mouth
* Esophagus
* Stomach.
LOWER DIGESTIVE SEGMENT
* Small and large intestines.
NB: This division is based on the distinctive functions of the
upper digestive segment (swallowing and digestion) and
lower digestive segment (absorption)
What are the main functions of the mouth and its associated salivary glands?
- Ingestion
- partial digestion
- lubrication of the food or bolus
The oral cavity includes
- Lips
- Cheeks
- Teeth
- Gums
- Tongue (Lingual papillae)
- Palate
Describe the epithelial lining of the oral mucosa and oral cavity
The oral mucosa is the mucous membrane lining the inside of
the mouth and consists of stratified squamous epithelium termed oral
epithelium and an underlying connective tissue termed lamina propria
The oral cavity is lined with stratified
squamous epithelium, keratinized or
nonkeratinized, depending on the region.
* The keratin layer protects the oral mucosa from damage during masticatory function and is best developed on the gingiva (gum) and
hard palate.
* Nonkeratinized squamous epithelium covers the soft palate, lips, cheeks, and the floor of the mouth.
Function of Oral mucosal
- Protection
- Sensation
- Secretion
- Thermal regulation
Function of Oral mucosal
- Protection
- Sensation
- Secretion
- Thermal regulation
Function of Oral mucosal
- Protection
- Sensation
- Secretion
- Thermal regulation
Function of Oral mucosal
- Protection
- Sensation
- Secretion
- Thermal regulation
Layers of the oral muscosa
Oral mucosa consists of two layers:
1. the surface stratified squamous epithelium and
2. the deeper lamina propria.
* The epithelium consists of four layers for the keratinized oral mucosa and the nonkeratinized has the two of
deeper four layers but does not have
the two superficial final layer.
* Stratum basale (basal layer)
* Stratum spinosum (prickle layer)
* Stratum granulosum (granular layer)
* Stratum corneum (keratinized layer)
Each of the organs on the digestive tract, is make up of four concentric layers which are?
(1) Mucosa (2) Submucosa (3) Muscularis Externa (4) Adventitia or
serosa.
Components of the mucosa
- a lining epithelium
- an underlying lamina propria consisting of a vascularized loose connective tissue
- a thin layer of smooth muscle, the muscularis mucosae.
Describe the esophagus
- is a muscular tube approximately 10 inches long that extends from the pharynx to the stomach.
- whose function is to transport food from the mouth to the stomach.
- It is located posterior to the trachea and in the mediastinum of the thoracic cavity.
Describe the layers of the esophagus
✓ The esophageal mucosa is lined by a stratified squamous nonkeratinized epithelium with stem cells scattered
throughout the basal layer overlying a lamina propria
* The lamina propria contains mucus-secreting esophageal cardiac glands
✓ Submucosa contains mucus-secreting esophageal glands proper whose secretions facilitate the transport of food and protect the mucosa
* The muscularis mucosae is not present in the upper portion of the esophagus, but it becomes organized near the stomach.
* The muscularis mucosae varies in thickness and is composed of a single longitudinal layer of smooth muscle.
✓ The upper third of the muscularis externa is composed only of skeletal muscle; the middle third is composed of a combination of smooth and skeletal muscle and the lower third is composed only of smooth muscle.
✓ Also, only the most distal portion of the esophagus, in the peritoneal cavity is covered by serosa.
* The rest is enclosed by a layer of loose connective tissue, the adventitia, which blends into the surrounding tissue
Components of the urinary system
Kidney
Ureter
Urinary bladder
Urethra
Describe the kidney and its divisions
Bean-shaped organs located retroperitoneally on the posterior abdominal wall
Kidney into capsule and parenchyma, parenchyma into cortex and medulla
Describe the kidney capsule
The capsule is made up of collagen fibres, some smooth muscle fibres and blood capillaries
Describe the kidney parenchyma
Parenchyma consists of millions of nephrons, branches of renal arteries, veins, lymphatics and nerves
What is a nephron?
This is the structural and functional unit of a kidney where filtration takes place
Classification of a nephron
On the basis of the location of their glomerulus:
1. Superficial (near the capsule)
2. Mid-cortical (near the medulla/ juxtamedullary)
On the basis of the loop of Henle:
1. Shorter looped: have superficial or mid-cortical glomerulus
2. Long looped
Components of the nephron
Glomerular capillaries
mesangium
bowman’s capsule
parietal layer
visceral layer
Nephron can be divided into the
renal corpuscle (or malpighian corpuscle) for filtration’
a long renal tubule for selective reabsorption (made up of PCT, DCT and loop of henle)
Describe the renal corpuscles
The renal corpuscle is the filtration apparatus of the nephron. Each corpuscle consists of the glomerulus and glomerular (Bowman’s) capsule.
The glomerulus is a network of capillaries formed by branches of the renal artery (afferent and efferent arterioles)
Discuss the glomerular capsule under podocytes, vascular pole and urinary pole
The glomerular capsule surrounds the glomerulus. It consists of two layers (parietal and visceral), which bound a cavity called the glomerular capsular space (Bowman’s / urinary space).
The inner visceral layer is made of special cells called podocytes. Podocytes cover the walls of glomerular capillaries, interdigitating with each other and forming narrow slits between their projections.
The outer parietal layer is made of simple squamous epithelium and is continuous with the nephron tubules. The afferent and efferent arterioles enter the renal corpuscle at the vascular pole, while the site where the glomerular capsule narrows and continues as the proximal thick segment of the nephron is called the urinary pole
What is the space between the parietal and visceral layer?
Urinary/ capsular space which is continuous with the lumen of the renal tubules
This space receives the fluid filtered through the capillary wall and visceral layer
Describe the PCT
- Urinary space continues as PCT at the urinary pole
- small lumen due to the brush border of micro-villi
- initial part is convoluted and present in the cortex
- terminal part is straight and descends into the medulla
-numerous mitochondria - both parts are lined by simple cuboidal epithelium resting on the basement membrane
- Functions in absorption and secretion
Describe the DCT
- The straight distal tubule (thick ascending limb) continues on from the thin ascending limb of the nephron loop. terminating in collecting tubule
- the convoluted distal tubule projects into the cortex
- Both parts of the distal tubule are composed of simple cuboidal epithelium
- It has a larger lumen and lesser in numner than PCT
Describe the nephron loop/ loop of henle
- the U-shaped bend of a nephron which extends through the medulla of the kidney.
- it consists of thin descending and thin ascending limbs composed of simple squamous epithelium.
- ## the two limbs work in parallel, with the surrounding vasa recta capillaries, to adjust the filtrate’s salt and water levels
Describe the collecting system
The collecting system of the kidney is a series of tubes that moves urine from the nephrons into the minor calyces. Several distal convoluted tubules from neighbouring nephrons drain into a collecting duct via connecting/collecting tubules.
Collecting ducts then travel through the kidney medulla, converging at the apex of each renal pyramid. Here, several ducts merge to form a single large papillary duct (of Bellini), which opens into the minor calyx through the area cribrosa
Lined by simple cuboidal epithelium
Types of collecting ducts and their epithelium
Cortical collecting ducts - simple cuboidal epithelium
Medullary collecting ducts - simple columnar epithelium
Papillary ducts - simple columnar epithelium (the demarcation of the different tubules is characterised by the change in epithelium)
Describe ureters
These are a pair of muscular tubes which conduct urine from the pelvis into the urinary bladder
3-4mm diameter
25-30cm length
Layers:
1. inner mucous membrane
2. middle smooth muscle layer
3. outer fibrous coat: adventitia
The mucosa of these organs is lined by
transitional epithelium
Consists of umbrella-shaped cells
Describe the layers of the ureter
Mucous membrane: consists of transitional epithelium, underlying dense irregular CT in the lamina propria
Muscle coat:
consists of 3 muscle layers (inner longitudinal, middle circular and outer longitudinal coat ( not in upper ureter))
Adventitia: outer fibrous coat of loose CT, contains numerous blood vessels, nerves, lymphatics and some fat cells
Describe the urinary bladder
A muscular bag where urine is stored temporarily and discharged periodically through the urethra during micturition
Histologically, the urinary bladder is lined with transitional epithelium and does not produce mucus
Describe the wall of the urinary bladder
Mucous membrane: Transitional epithelium which is urine-proof, devoid of muscularis mucosae with umbrella cells
The mucous membrane consists of folds when empty and disappear in a distended bladder
Lamina propria: Dense CT with coarse collagenous fibres
Submucosa
Muscular coat: smooth muscle (detrusor muscle)
Seroud layer/adventitia
Describe the wall of the urinary bladder
Mucous membrane: Transitional epithelium which is urine-proof, devoid of muscularis mucosae with umbrella cells
The mucous membrane consists of folds when empty and disappear in a distended bladder
Lamina propria: Dense irregular CT with mucus glands
Submucosa: consists of areolar tissue
Muscular coat: 3 smooth muscle layers
Seroud layer/adventitia
consists of the detrusor muscle, internal and external sphincter
Adventitia
Describe the urethra
The tube that carries urine from bladder to exterior:
composed mucus membrane, submucosa and muscular layer
Female urethra
Purely urinary organ
Function of the kidney
Urine production; maintains body fluid and electrolyte balance, blood pressure, acid base balance
Describe the juxtaglomerular apparatus
Nestled into the vascular pole of the nephron is a collection of cells called the juxtaglomerular apparatus (JGA). It is formed by 3 types of cells; macula densa, juxtaglomerular granular (JG) cells and extraglomerular mesangial (Lacis) cells
They are responsible for the production of renin in response to low BP
Describe the Bowmans capsule