A&P Exam 3

The major functions of the skeletal system

1. Support and Protect

2. Movement

3. Blood formation

4. Mineral Storage

The classes of bones.

1. Long Bone

2. Short Bone

3. Flat Bone

4. Irregular Bone

5. Sesamoid Bone

what is the diaphysis of a long bone?

The Shaft

What is the epiphysis of a long bone?

The ends

what is the metaphysis of a long bone?

The region between the diaphysis and epiphysis.

All the parts of a Long Bone

1. Diaphysis and Epiphysis

2. Compact Bone

3. Spongey Bone

4. Red Bone Marrow

5. Yellow Bone Marrow

6. Epiphyseal Plate/Line

The 4 types of bone cells

1. Osteoprogenitor cells

2. Osteoblasts

3. Osteocytes

4. Osteoclasts

what does the Osteoprogenitor cells do?

precursor cells that develop into osteoblasts.

what does the Osteoblasts do?

build new bone.

what does the Osteocytes do?

mature bone cells that maintain bone tissue.

what does the Osteoclasts do?

break down bone tissue.

Osteoprogenitor cells

Found in the Periosteum (the outer covering of bone) and the Endosteum (the lining of the inner bone surfaces).

Endochondral ossification

the process in which bone replaces cartilage.

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Osteon

The functional unit of compact bone. Concentric circles of bone surrounding a central canal.

Bone

1. Hard and mineralized Matrix

2. Contains: Osteoblasts, osteocytes, osteoclasts, osteoprogenitor cells

3. Structure: Compact bone and spongy bone

4. Has a blood supply

5. Replaces Cartilage

Cartilage

1. Firm and Flexible Matrix

2. Contains: Chondroblasts and chondrocytes

3. Has no osteons

4. Lacks blood vessels

5. Acts as the starting model

Central Canal

The inner part of the osteon. Houses the blood vessels and nerves.

Perforating canal

“Sideways bits for blood and nerves.”

Location of blood vessels and nerves

In the central and perforating canals.

Lacuna

“the hole”

Trabeculae

The main unit of spongy bone.

Compact Bone

Contains osteons, which help organize the hard, dense tissue

Spongy Bone

Organized into a network of trabeculae, rather than the typical osteons found in compact bone.

Intramembranous Ossification

bone forms directly from mesenchymal tissue, without first forming a cartilage model.

Endochondral ossification

1. A cartilage model is present.

2. The cartilage calcifies.

3. Osteoblasts deposit bone.

4. Osteoclasts remove bone from the center, creating the medullary cavity.

5. Bone formation continues as the bone develops.

6. The epiphyseal growth plate eventually closes.

Intramembranous ossification

1. Mesenchymal cells secrete osteoid, the material that forms the initial bone matrix.

2. Osteoblasts spread bone material from ossification centers as the matrix calcifies.

3. Osteocytes and osteoclasts help organize the bone, including forming trabeculae of spongy bone.

4. Compact bone and the periosteum develop.

Mesenchymal tissue

early type of connective tissue in the body that can develop into different types of tissues, including bone.

Growth in width

Appositional growth.

Growth in length

Epiphyseal plate

Bone remodeling

the ongoing process of removing old bone and adding new bone. It helps bones adapt to the forces placed on them.

PTH (parathyroid hormone), Calcitriol (active vitamin D), and Calcitonin

What 3 hormones help regulate the amount of calcium in your blood?

PTH (parathyroid hormone)

Signals the body to raise blood calcium when it is too low. (Increases calcium in blood.) - CALCIUM UP

Calcitriol (active vitamin D)

Helps the intestines absorb more calcium from food. (Increases calcium in blood) -CALCIUM ABSORBTION

Calcitonin

Helps reduce blood calcium, mainly by inhibiting osteoclast activity. (Decreases calcium in blood) - CALCIUM DOWN

bone growth

developing or increasing bone size

calcium regulation

controlling the amount of calcium in the blood.

Growth hormone (GH)

Promotes bone growth, especially during childhood.

Thyroid hormone

Supports normal skeletal growth and development.

Sex hormones (estrogen and testosterone)

Promote growth during puberty and help close growth plates.

Glucocorticoids

Excess levels can inhibit bone formation and growth.

Serotonin

Effects on bone are complex and depend on where it acts.

Calcitriol

Supports bone mineralization by helping the body absorb calcium and phosphate.

PTH

Regulates calcium; sustained high levels can increase bone breakdown, while intermittent signaling can support bone formation.

Calcitonin

Inhibits osteoclast activity, reducing bone breakdown.

nephron

The functional unit of the kidney that filters blood and helps produce urine.

Glomerulus

a cluster of capillaries that filters blood.

Glomerular (Bowman’s) capsule

surrounds the glomerulus and collects the filtrate.

Proximal convoluted tubule (PCT)

Reabsorbs most of the water and useful substances from the filtrate.

Loop of Henle

helps establish the concentration gradient needed to concentrate urine.

Distal convoluted tubule (DCT)

adjusts the amounts of ions and water reabsorbed or secreted.

Collecting duct

Makes final adjustments to water reabsorption and carries urine toward the renal pelvis.

Blood supply around the nephron

Blood enters the glomerulus through the afferent arteriole and leaves through the efferent arteriole. The efferent arteriole then supplies capillaries around the tubules or the vasa recta, depending on the nephron.

Renal corpuscle, and Renal tubule

what are the two main parts of the kidney that filters blood and concentrates waste.

Renal tubule

Where useful materials are reabsorbed into the blood and the filtrate is adjusted to concentrate waste.

Renal corpuscle

Where waste, ions, and other molecules are initially filtered out of the blood to create filtrate.

Proximal convoluted tubule (PCT)

Reabsorbs most of the useful materials and much of the water and ions

Descending loop of Henle

allows water to leave the tubule.

Ascending loop of Henle

moves salts out of the tubule but does not allow water to follow.

Distal convoluted tubule (DCT)

makes further adjustments to the filtrate, including hormone-regulated changes.

Collecting duct

collects the tubular fluid and adjusts how much water is reclaimed. Your instructor’s slides note that it is not technically part of the nephron.

What are the parts of the renal tubule

• Proximal convoluted tubule (PCT)

• Descending loop of Henle

• Ascending loop of Henle

• Distal convoluted tubule (DCT)

• Collecting duct

Filtration:

Water and small substances move from the blood in the glomerulus into the glomerular capsule, forming filtrate. Large proteins and blood cells normally stay in the blood. BLOOD —> TUBULE

Tubular reabsorption

Useful substances, such as nutrients, water, and ions, move from the filtrate in the renal tubule back into the blood so the body can keep them.

TUBULE —> BLOOD

Tubular secretion

Additional substances, such as certain drugs and wastes, move from the blood into the renal tubule to be eliminated in urine. BLOOD —> TUBULE (additional substances added to filtrate)

Glomerular hydrostatic pressure

Blood pressure inside the glomerulus pushes fluid out of the blood and into the glomerular capsule.

Blood colloid osmotic pressure

Proteins in the blood pull water back toward the blood, opposing filtration.

Capsular hydrostatic pressure

Fluid already in the capsule pushes back against incoming fluid, also opposing filtration.

GCP (HPg)

Glomerular capillary hydrostatic pressure — pushes fluid out of the blood and into the capsule.

BCOP

Blood colloid osmotic pressure — pulls water back into the blood.

CHP

Capsular hydrostatic pressure — pushes against fluid entering the capsule.

Net filtration pressure (NFP)

The overall pressure that determines whether fluid moves out of the glomerulus and into the glomerular capsule. (NFP = GCP - BCOP - CHP)

GFR (glomerular filtration rate)

The amount of fluid filtered from the blood into the glomerular capsules over a certain amount of time.

Afferent arteriole dilates (widens)

More blood can flow into the glomerulus, increasing pressure and generally INCREASING GFR.

Afferent arteriole constricts (narrows):

Less blood flows into the glomerulus, decreasing pressure and generally DECREASING GFR.

Mechanism of Urine Creation by the Nephron

Urine is formed through filtration, reabsorption, and secretion. Filtration moves water and small substances from the blood into the nephron. Reabsorption moves useful substances from the tubule back into the blood, while secretion moves additional substances from the blood into the tubule to be removed in urine.

Proximal convoluted tubule (PCT)

• Reabsorption: Reabsorbs most of the useful substances, including nutrients, proteins, large amounts of water, and ions.

• Secretion: Secretes some drugs and nitrogenous wastes, such as urea.

• Hormones: PCT is the main site of bulk reabsorption and secretion.

Descending limbs of the Loop of Henle

• Reabsorption: Permeable to water, so water passively leaves the tubule and enters the surrounding tissue and blood.

• Secretion: The slides state that nothing is secreted in the Loop of Henle.

• Main idea: Water leaves the descending limb.

Ascending limb limbs of the Loop of Henle

• Reabsorption: Salts are actively moved out of the tubule and picked up by the blood.

• Water: This limb is impermeable to water, so water cannot follow the salts out.

• Secretion: The slides state that nothing is secreted in the Loop of Henle.

• Main idea: Salts leave the ascending limb, helping create the concentration gradient in the kidney medulla.

Distal convoluted tubule (DCT)

• Reabsorption and secretion: Makes final adjustments to the tubular fluid. Some substances are reabsorbed, while others are secreted.

• ANP (atrial natriuretic peptide): Decreases sodium reabsorption, so more sodium is excreted. Water follows sodium, increasing water loss in urine. ANP also increases GFR.

• Aldosterone (ALDO): Increases sodium reabsorption. Water follows sodium, helping the body retain water and salts.

• ADH (antidiuretic hormone): Primarily increases water reabsorption in the collecting duct, rather than being described as a main DCT effect in the slides.

• PTH (parathyroid hormone): Its specific effect on the DCT is not explained in the provided slides.

• pH: The slides focus on pH regulation in the collecting duct rather than the DCT.

Collecting duct

• Reabsorption: Water can be reabsorbed here, depending on whether the body needs to conserve water.

• ADH: Causes aquaporins (water channels) to be inserted into the collecting duct’s principal cells. More aquaporins allow more water to be reabsorbed into the body, producing more concentrated urine. With less ADH, fewer aquaporins are present, less water is reabsorbed, and urine becomes more dilute.

• ANP and aldosterone: Their effects on sodium reabsorption influence how much water the body excretes or retains, as described above.

• PTH: The provided slides do not specify its effect on the collecting duct.

Type A cells

Reabsorb bicarbonate HCO3- and secrete hydrogen ions H+, lowering pH.

Type B cells

• Reabsorb hydrogen ions and secrete bicarbonate, raising pH.

• Secretion: Hydrogen ions can be secreted into the tubule to help regulate pH.

ANP

Less sodium reabsorption → more sodium and water excreted

ADH

More aquaporins → more water reabsorbed → concentrated urine

PTH

The provided slides do not explain its specific effects on these nephron sections

Aldosterone

More sodium reabsorbed → water and salts retained

ADH is present

More aquaporins are added to the collecting duct, allowing more water to be reabsorbed into the blood. You make less, more concentrated urine.

ADH is reduced

Less water is reabsorbed, so you make more, dilute urine.

Alcohol (ethanol)

Reduces ADH release, so your body reabsorbs less water and produces more urine.

ADH

Adds water back to then body

How is the kidney’s concentration gradient established, and how does ADH help concentrate urine?

The Loop of Henle creates the gradient: the descending limb loses water, while the ascending limb moves salts out but not water. ADH adds aquaporins to the collecting duct, allowing more water to be reabsorbed and producing concentrated urine. Less ADH means more dilute urine.

What is specific gravity, and how does it relate to hydration and urine concentration?

Specific gravity measures urine density compared with water. Higher specific gravity means more concentrated urine and usually indicates dehydration. Lower specific gravity means more dilute urine and usually indicates better hydration.

The micturition reflex

As the bladder fills, stretch receptors signal that it is full. The parasympathetic nervous system causes the detrusor muscle to contract and the internal urethral sphincter to relax. When a person is ready to urinate, they voluntarily relax the external urethral sphincter, allowing urine to leave the bladder.