3- Body Fluids

Body fluids

liquid components within a living organism

General body fluid composition

-water

-gases (O2, CO2)

-Hormones

-Electrolytes

-Waste products

-Nutrients (proteins, sugars, etc.)

The composition of each type of body fluid varies depending on location and function.

Maintaining body fluid balance is critical for homeostasis.

Body water composition

Total body water = total amount of fluid/water in the body. Accounts for 50-70% of body weight. 18% proteins/related substances, 15% fats (females > males), 7% minerals

What does total body water inversely correlate with?

Body fat

-TBW is a higher % of body weight when body fat is low

-TBW is lower % of body weight when body fat is high

-Females have less body water than males due to higher adipose tissue %

-Thin men have the highest water body weight percentage (~70%)

-Obese women have the lowest water body weight percentage (~50%)

What are the two major compartments of total body water?

Intracellular Fluid (ICF) and Extracellular Fluid (ECF)

What fraction of total body water is found in the intracellular fluid?

Approximately 2/3

What fraction of total body water is found in the extracellular fluid?

Approximately 1/3

What is the 60-40-20 Rule regarding body water distribution?

60% of body weight is water, 40% is ICF, and 20% is ECF

What are the two minor compartments of extracellular fluid?

Interstitial fluid and Plasma

What is the role of body fluids in the body?

Body fluids transport nutrients, waste products, and hormones throughout the body.

What determines which materials are exchanged through body fluids?

Different organ/organ systems determine which materials will be exchanged through the body fluid.

What is the role of interstitial fluid in nutrient exchange?

Nutrients diffuse from capillaries to interstitial fluid to intracellular fluid (ICF).

How is waste removed from cells in the body?

Waste diffuses from intracellular fluid (ICF) to interstitial fluid to capillaries.

How does interstitial fluid assist with cell communication?

Interstitial fluid assists with cell-to-cell signaling through gap junctions.

Intracellular fluid

a complex solution containing water, dissolved solutes (ions, electrolytes, and other molecules), and proteins inside cells

-Major cations = Potassium, Magnesium

-Major anions - Proteins, Organic phosphates (ex., ATP, ADP, AMP)

-Fluid within a cell's cytoplasm/cytosol

What divides the ICF from the ECF?

cell membranes

ICF functions

-Facilitates cellular metabolism

-Allows for intracellular communication

-Maintains cell volume/shape

What is extracellular fluid?

Water and solutes outside of cells, separated into two compartments.

What is plasma?

The aqueous component of blood, making up 55% of blood volume.

-Extracellular fluid

What is interstitial fluid?

Fluid that bathes body cells; an ultrafiltrate of plasma, nearly the same composition as plasma but missing plasma proteins and RBCs.

-Extracellular fluid

What is the major cation in interstitial fluid?

Sodium.

What are the major anions in interstitial fluid?

Chloride and Bicarbonate.

What divides the interstitial fluid from the plasma?

capillary walls

ECF functions

-Exchange medium for substances entering/exiting cells

-Allows for fluid and electrolyte balance

-Facilitates nutrient and waste transport

Sodium (Na+)

Most abundant in ECF (90% of extracellular cations)

-Plays pivotal role in fluid and electrolyte balance (50% of ECF osmolarity)

Chloride (Cl-)

Most prevalent anion in ECF

-Moves between ECF and ICF due to Cl- transporters (Cl- shift)

Potassium (K+)

Most abundant cation in ICF (Maintains ICF fluid volume)

-Helps regulate pH when exchanged with H+; Resting potential

Bicarbonate (HCO3-)

The second most prevalent extracellular anion.

Exchanged with Cl- (Cl- shift) across and RBC membrane to help maintain the correct balance of anions in ECF/ICF

Intracellular fluid

-Primarily water, with high concentrations of potassium, magnesium, and phosphate

-Slightly more acidic, with a pH between 6.8 and 7.4

-Support cell function, intracellular communication, and transports gases, nutrients, and other molecules

Extracellular Fluid

-Primarily water, with high concentrations of sodium, chloride, bicarbonate, oxygen, glucose, fatty acids, and amino acids

-Slightly more alkaline, with a pH between 7.3 and 7.5

-Facilitates the exchange of substances between cells and their distribution tissues, acts as a medium for nutrient and waste transport, and maintains osmotic pressure

What are some specialized extracellular fluids that protect, nourish, lubricate, or cushion structures throughout the body?

-Lymph

-Synovial fluid

-Vitreous body

-Tears, sweat

-Cerebrospinal fluid

-Endolymph

-Perilymph

-Pleural, pericardial, and peritoneal fluids

The purpose/function of these extracellular fluids varies based on the primary structure they support

What is the aqueous humor?

Fluid that fills the anterior chamber of the eye.

What secretes the aqueous humor?

The ciliary body.

How does aqueous humor enter the anterior chamber?

Through the pupil.

What is the function of aqueous humor?

Nourishes the endothelial cells of the cornea and keeps the eye inflated.

Where does aqueous humor drain?

Through the trabecular meshwork at the angle of the anterior chamber.

What condition can result from blockage of aqueous humor flow?

Glaucoma due to increased intraocular pressure.

Vitreous humor

-The posterior chamber of the eye is filled with vitreous humor

-Contains a gel (vitreous body of hyaluronic acid separated by the retina)

-Occupies space, allows transmissibility, pushes against retina

Tears

-Produced by lacrimal glands

-Isotonic, but becomes hypertonic due to evaporation as the fluid passes over the cornea

-When the tear flow is copious, the fluid is isotonic

-Under stimulus with a slow rate of tear flow, the fluid is about 25 mOsm hypertonic

-pH = 7 to 7.6 due to loss of CO2

-Protein content is 0.6 to 0.18 g/dl with an albumin/globulin ratio of 1:5 to 2:1

-Layers of mucin and oil are also present

Lysozyme

protects the eye from infectious agents (lyses microorganism cells)