Unit 6

Microanatomy of the kidney

Microanatomy of the kidney

functional anatomy of the kidney

• nephrons, collecting tubules, collecting ducts (and associated structures)

Nephron

• Microscopic functional filtration unit of kidney

• consists of: renal corpuscle and renal tubule

• all of corpuscle and most of tubules reside in cortex

Renal corpuscle

• Enlarged bulbous region of nephron within renal cortex

• composed of glomerulus and glomerular capsule

Glomerulus

• a tangle of capillary loops, glomerular capillaries

• blood enters via afferent arteriole

• blood exits via the efferent arteriole

Glomerular capsule

• internal permeable visceral layer

• external impermeable parietal layer

• capsular space between two layers

Renal tubule

1.) Proximal convoluted tubule (PCT)

2.) Nephron Loop

3.) distal convoluted tubule (DCT)

PCT

• First region of the renal tubule

• originates at the tubular pole of the renal corpuscle

• simple cuboidal epithelium

• Microvilli increase surface area and reabsorption capacity

Nephron loop

• Originates at a sharp bend in PCT

• descending limb: extends medially from PCT

• ascending limb: returned to renal cortex and ends at DCT

• Hairpin turn

DCT

• Originates in the renal cortex at the end of ascending limb

• extends to collecting tubule

• lined by simple cuboidal epithelium without microvilli

• appears clear when viewed with a light microscope

Mictrurition

expulsion of urine from the bladder

• associated with two reflexes: storage and micturition

Storage reflex

continuous sympathetic stimulation

• causes relaxation of the detrusor to accommodate urine

• stimulates contraction of the internal urethral sphincter

Micturition reflex

• the volume of urine in the bladder is between 200-300mL

• Visceral sensory neurons signaled by baroreceptors

Micturition center

• alter’s nerve signals down the spinal cord through pelvis splanchnic nerves

Urine production

Filtration, reabsorption, and secretion

Glomerular filtration

• in glomerular capillaries

• separates some water and dissolved solutes from blood plasma

• water and solutes enter the capsular space of the renal corpuscle

• separated fluid is called filtrate

Tubular reabsorption

• Movement of components within the tubular fluid

• move by diffusion, osmosis, or active transport

• return to blood within peritubular capillaries and vasa recta

• all vital solutes and most water reabsorbed

• waste product, excess solutes, and some water remains

Tubular secretion

• Movement of solutes, usually by active transport

• move out of blood within peritubular and vasa recta capillaries

• move into tubular fluid

• the material moved selectively into tubules to be excreted

Upper GI Tract

Oral cavity, salivary glands, tongue, teeth, pharynx, esophagus, stomach

Oral Cavity + salivary glands

• mechanical digestion begins

• saliva is secreted from salivary glands in response to food

• contains salivary amylase, an enzyme initiating the digestion of starch

  • mixed with ingested materials to form a bolus

Tongue

• Manipulates and mixed materials during chewing

  • important functions in swallowing and speech

Teeth

Grinding and crushing material in mouth

Dentin

primary mass of tooth

Enamel

external surface of teeth

Pulp cavity

center of tooth filled with CD and pulp

Root cancal

continuous with pulp cavity, opens to tissue around

Pharynx

• Bolus moved to the pharynx during swallowing

  • mucus secreted to facilitate swallowing

Esophagus

• Bolus transported form the pharynx into the stomach

• lubricated by mucus secretions

Stomach

• bolus mixed with gastric secretions by smooth muscle contraction

• secretions produced by epithelial cells of the stomach

• chyme formed from mixing

• regions: fundus, body, pylorus

Lower GI tract

small intestine, large intestine, liver, gallbladder, pancreas

small intestine

• divided into three regions: duodenum, jejunum, ileum

• receives chyme from stomach mixed with accessory organ secretions

  • most chemical digestion and absorption happen here

Duodenum

• the first segment of the small intestine

• receives chyme from the stomach

  • receives accessory gland secretions from the liver, gallbladder, and pancreas

Jejunum

• the middle region of the small intestine

• two fifth of the total length of the small intestine

• primary region for chemical digestion and nutrient absorption

Ileum

• last region of the small intestine

• forms three-fifths of the small intestine

  • continues absorptions of digested material

Large intestine

• primarily absorbs water, electrolytes, and some vitamins

• feces produced and eliminated through the anus

Cecum

• intraperitoneal blind sac in the right lower abdominal quadrant

• chyme entering from the ileum

veriform appendix

harbors beneficial bacteria

colon

• the second portion of the large intestine

• has four segments: ascending transverse, descending, sigmoid (self-explanatory)

Rectum

Muscular tube that expands to store feces

Liver

• accessory digestive organ and the largest internal organ

• right upper quadrant of the abdomen immediately inferior to the diaphragm

Gallbladder

• saclike organ attached to the inferior surface of the liver

• stores concentrate and release bile produced in the liver

Pancreas

• Produces and secrete insulin and glucagon

• produces pancreatic juice to assist with digestive activities

Digestion

• breakdown of ingested food into smaller structures

• two types: mechanical + chemical

Mechanical digestion

Material physically broke down by chewing and mixing

Chemical digestion

Involved specific enzymes to break chemical bonds

absorption

• transport of digested molecules, electrolytes, vitamins, water

• move from the GI tract into blood or lymph

Elimination

expulsion of indigestible components that are not absorbed

Mixing

• Backward and forward motion that lacks directional movement

• blends ingested materials with secretions

Propulsion

direction movement of materials through GI tract

Coitus

sexual intercourse

Ovulation

release of an egg from the ovary

Fertilization

• two gametes fuse to form a new diploid cell

• restores the diploid number of chromosomes

• determines the sex of an organism

• initiates cleavage

Puberty

• External sex characteristics become more prominent such as breast enlargement in females

• pubic hair growth in both sexes and fully functioning reproductive organs in both sexes

• gonads start to secrete their sex hormones and gametes begin to mature within gonads

Menarche

Person’s first menstrual cycle

Menopause

When a woman has stopped having monthly menstrual cycles for a year and is not pregnant

lactation

production and release of breast milk from mammary glands

Ejaculation

when semen is released during intercourse

Implantation

attachment of the fertilized egg or blastocyst to the wall of the uterus at the start of pregnancy

parturition

action of giving brith to young, childbirth

Postpartum

following childbirth or the birth of young

Mastication

• Chewing

• mechanically reduces bulk to facilitate swallowing

• increases surface area to facilitate exposure to digestive enzymes

• promotes salivation

Deglutition

• Swallowing

• Moving ingested materials from the oral cavity to the stomach: 3 phases

Digestion

• Breakdown of ingested food into smaller structures

• Change large complex molecules into smaller molecules

Defecation

Elimination of feces

Genotype

Genetic makeup of an individual

Phenotype

Physical expression of genotype

Flow of Urine

Urinary tract: ureters, urinary bladder, urethra

Ureters

• long epithelial-lined fibromuscular tubes

• conduct urine from the kidney to the urinary bladder

• Retroperitoneal

• originate from the renal pelvis as it exits the hilum of the kidney

Urinary bladder

• expandable, muscular container

• reservoir for urine

• inverted pyramidal shape when empty

Trigone

• posterior triangular area of the bladder wall

• funnel to direct urine into the urethra

• common with infections

• remains immobile as the bladder fills and empties

Urethra

• Epithelial-lined fibromuscular tube

• exits the urinary bladder through the urethral opening

• conducts urine to the exterior of the body

Internal urethral sphincter

• Involuntary, superior sphincter

• formed by skeletal muscle fibers of the pelvic diaphragm

• voluntary sphincter controlled by the somatic nervous system

• Learn muscle control of muscle during toilet training

Flow of food

Oral cavity → pharynx → esophagus → stomach → small intestine → large intestine

Movement of gametes

sperm migrate through the cervical mucus and travel about 2-3 millimeters per minute aided by contractions of the uterine and cervical muscles

Carbohydrates

• catalyzed by salivary amylase from salivary glands

• broken down in the small intestine by pancreatic amylase

• Maltase breaks bonds between the two glucose molecules

Proteins

• broken down by enzymes

• digestion releases individual amino acids

• begins with the stomach lumen with pepsin

• broken down by trypsin and dipeptidase in the small intestine

lipids

• broken down in the stomach by lingual lipase and gastric lipase

• gastric lipase in the stomach

• pancreatic lipase in the small intestine

Oxytocin

• increased levels produced by the hypothalamus

• involved in uterine contractions

• involved in milk expulsion from mammary glands

• increase in the second and third trimesters

female Gametes

• Oocyte

• single gamete monthly

Male gametes

• 100 million/day

• stored for a short time only

• if not expelled form the body, they are reabsorbed

Meiosis

• sex cell division

• 4 haploid daughter cells genetically different from parent cells

• includes crossing over

• get genes from both parents on one chromosome

Interphase

• cell phase prior to meiosis

• DNA on each cell replicated

• replicated chromosomes now composed of two sister chromatids

Calculi

• kidney stones

• formed by crystalline minerals building up in the kidney

• more common in males

• most pass on their own in less than 4mm diameter

• may require lithotripsy

UTI

• occurs when bacteria or fungi multiply within the urinary tract

• women are more prone due to short urethra

• often first develops in the urethra

• diagnosed through urinalysis

• treated with antibiotics

Gerd

• inflammation of the esophagus due to acidic chyme refluxing into the esophagus

• pain posterior to the sternum, heartburn

• treatment: lifestyle changes

• can result from chronic reflux

• build-up of scar tissue

Barrett esophagus

• Change from stratified squamous to columnar secretory epithelium

• increase risk of cancerous growth

Vomiting

• rapid expulsion of gastric contents through the oral cavity

• controlled by the vomiting center in the medulla oblongata

• closure of nasal passages and glottis

• gastric contents forced through the esophagus

Cirrhosis of liver

• hepatocytes replaced by fibrous scar tissue

• compresses blood vessels

• compresses bile ducts in the liver

• caused by chronic injury to hepatocytes (chronic alcoholism)

Diarrhea

disruption of normal mechanism to absorb intestinal water

Nondisjunction

• Failure of separation of homologous chromosomes or sister chromatids

• Gamete with 22 or 24 chromosomes

• Resulting gamete

• May have 47 chromosomes (trisomy)

• Individuals with 3 copies of one chromosome

• May have 45 chromosomes (monosomy)

• An individual with 1 copy of a chromosome

Tubal pregnancy

• One type of ectopic pregnancy

• Fertilized egg implants in the uterine tube

• Unable to expand as the embryo grows

• Embryo viable only until week 8

• Uterine wall ruptures if the embryo is not removed

• Hemorrhage and loss of life are possible

STI

• Groups of infectious diseases transmitted via sexual contact

• STIs are transmitted because symptoms go unnoticed

• Condoms help prevent spread but not 100%

• A leading cause of pelvic inflammatory disease in women

• This can lead to blockage of tubes and infertility

Chlamydia

• Most frequently reported in the U.S.

• Due to the Chlamydia trachomatis bacterium

• Most people asymptomatic

• May have symptoms of vaginal discharge, painful urination, back pain

• Treated with antibiotics

genital herpes

• Caused by herpes simplex virus

• Cyclic outbreaks of blister formation in genital and anal regions

• No cure; antiviral medications lessen the severity and length

Gonorrhea

• Caused by bacterium Neisseria gonorrhoeae

• Spread by sexual contact or from mother to baby during delivery

• Treatment with antibiotics

syphilis

• Caused by bacterium Treponema pallidum

• Spread sexually via contact with a syphilitic sore, chancre, or in utero

• Treatment with antibiotics

vertex position

• Head down; face toward the sacrum

• Ideal position for dilating the cervix and pushing fetus through vagina

Breech position

• Buttocks first

• May delay cervical dilation

Variant position

• Forceps, a vacuum may be needed.

  • Cesarean section: Fetus delivered through an abdominal incision

Mitosis

• Somatic cell division

• produces 2 diploid daughter cells genetically identical to parent cells

• no crossing over

female gamete movement

uterine tubes → infundibulum → ampulla → isthmus → uterine part of tube → wall of uterine tube