Unit 2

recombinant chromosomes

individual chromosomes that carry genes (DNA) from two different parents

testes

male gonads that produce sperm in highly coiled tubes

seminiferous tubules

highly coiled tubes that sperm are produced in

scrotum

a fold of the body wall that maintains testis temperature below the core body temperature

epididymis

the coiled duct that sperm pass through from the seminiferous tubules of a testis

vas deferens

during ejaculation, the sperm are propelled from each epididymis through this muscular duct

urethra

the outlet tube for both the excretory system and the reproductive system. this tube runs through the penis and opens to the outside at the tip of the penis

penis

this contains the urethra as well as three cylinders of spongy erectile tissue. During sexual arousal, the erectile tissue fills with blood from the arteries. As this tissue fills, the increasing pressure seals off the veins that drain this part, causing it to engorge with blood

What can cause erectile dysfunction?

alcohol consumption, certain drugs, emotional issues, and aging

glans

the head of the penis that has a much thinner outer layer that than the main shaft and is consequently more sensitive to stimulation

prepuce

the foreskin. Surrounds the human glans and is removed if a male is circumcised

ovaries

the female gonads that flank the uterus and are held in place in the abdominal cavity by ligament

oocyte

a partially developed egg

oviduct

the fallopian tube. extends from the uterus toward a funnel-like opening at each ovary

uterus

the womb. a thick, muscular organ that can expand during pregnancy to accommodate a 4-kg fetus

endometrium

the inner lining of the uterus. it is richly supplied with blood vessels

cervix

the neck of the uterus that opens into the vagina

vagina

a muscular but elastic chamber that is the site for insertion of the penis and deposition of sperm during copulation

vulva

the collective term for the external female genitalia

labia majora

a pair of thick, fatty ridges that enclose and protect the rest of the vulva

labia minora

a pair of slender skin folds that border the cavity that holds the vaginal opening and the separate opening of the urethra.

clitoris

consists of erectile tissue supporting a rounded glans, or head, covered by a small hood of skin, the prepuce

mammary glands

present in both sexes, but normally produce milk only in females

gametogenesis

the production of gametes

spermatogenesi

the formation and development of sperm

oogenesis

the development of mature oocytes (eggs)

conception

fertilization. occurs when a sperm fuses with an egg in an oviduct

blastocyst

a sphere of cells surrounding a central cavity produced 5 days after fertilization

human chorionic gonadotropin (hCG)

an embryonic hormone that acts like pituitary LH in maintaining secretion of progesterone and estrogens through the first few months of pregnancy. Some of this passes from the maternal blood to the urine, where it can be detected by the most common early pregnancy tests

trophoblast

the outer layer of the blastocyst, which grows outward and mingles with the endometrium

placenta

this disk-shaped organ, containing both embryonic and maternal blood vessels, can weigh close to 1 kg at birth

organogenesis

the development of the body organs. The first trimester is the main period of this.

What are the three stages of labor?

1. The thinning and opening up of the cervix.
2. The expulsion, or delivery, of the baby
3. Delivery of the placenta

transport proteins

proteins that span the membrane and hydrophilic substances pass through to avoid contact with the lipid bilayer

aquaporins

Channel proteins that greatly facilitate the passage of water molecules through the membrane in certain cells. Each of these allows entry of up to 3 billion water molecules per second, passing single file through its central channel, which fits ten at a time.

diffusion

the movement of particles of any substance so that they spread out into the available space

What is a simple rule of diffusion?

In the absence of other forces, a substance will diffuse from where it is more concentrated to where it is less concentrated.

concentration gradient

the region along which the density of a chemical substance increases or decreases. Any substance will diffuse down this.

passive transport

the diffusion of a substance across a biological membrane

osmosis

the diffusion of free water across a selectively permeable membrane, whether artificial or cellular

tonicity

the ability of a surrounding solution to cause a cell to gain or lose water

osmoregulation

the control of solute concentrations and water balance

turgid

when a cell is very firm. The healthy state for most plant cells

flaccid

when a cell becomes limp. This happens if a plant’s cells and surroundings are isotonic, there is no net tendency for water to enter

plasmolysis

When a cell loses water to its surrounding and shrinks. Its plasma membrane pulls away from the cell wall at multiple places

facilitated diffusion

when polar molecules and ions impeded by the lipid bilayer of the membrane diffuse passively with the help of transport proteins that span the membrane

ion channels

channel proteins that transport ions

gated channels

many ion channels function as these. They open or close in response to a stimulus.

active transport

When a cell must expend energy to pump a solute across a membrane against its gradient

sodium-potassium pump

a transport system that exchanges sodium for potassium across the plasma membrane of animal cells

membrane potential

the voltage across a membrane

electrochemical gradient

the combination of forces acting on an ion

electrogenic pump

a transport protein that generates voltage across a membrane

proton pump

the main electrogenic pump of plants, fungi, and bacteria, which actively transports protons out of the cell

cell body

where most of a neuron’s organelles, including its nucleus are located

dendrites

numerous highly branched extensions that stud the cell body in a typical neuron. These receive signals from other neurons

axon

an extension that transmits signals to other cells

synapse

the junction from which each branched end of an axon transmits information to another cell

neurotransmitters

chemical messengers that pass information from the transmitting neuron to the receiving cell

glial cells (glia)

supporting cells required by the neurons of vertebrates and most invertebrates

sensory neurons

transmit information about the external stimuli such as light, touch, or smell or internal conditions such as blood pressure or muscle tension

interneurons

form the local circuits connecting neurons in the brain or ganglia. Responsible for the integration of sensory input

motor neurons

transmit signals to muscle cells, causing them to contract

nerves

formed by the axons of neurons bundled together

regulator

an animal is this for an environmental variable if it uses internal mechanisms to control internal change in the face of external fluctuation

conformer

an animal is this if it allows its internal condition to change in accordance with external changes in the particular variable

homeostasis

the maintenance of internal balance

set point

the particular value that an animal maintains to achieve homeostasis

negative feedback

a control mechanism that damps its stimulus

positive feedback

a control mechanism that amplifies the stimulus

circadian rhythm

a set of physiological changes that occur roughly every 24 hours

acclimatization

an animal’s physiological adjustment to changes in it external environment

circulatory fluid, a set of interconnecting vessels, and a muscular pump (the heart)

the three basic components of a circulatory system

open circulatory system

system where the circulatory fluid, called hemolymph, is also the interstitial fluid that bathes body cells

closed circulatory system

system where the circulatory fluid called blood is confined to vessels and is distinct from intestinal fluid

arteries, veins, and capillaries

the three main types of blood vessels

arteries

carry blood from the heart to organs throughout the body

arterioles

arteries branch into these within organs. These small vessels convey blood to capillaries

capillaries

microscopic vessels with very thin, porous walls

capillary beds

networks of capillaries that infiltrate tissues, passing within a few cell diameters of every cell in the body

veins

the vessels that carry blood back to the heart

atria

the chamber that receives blood entering the heart

ventricle

the chamber responsible for pumping blood out of the heart

single circulation

in sharks, rays, and bony fishes, blood travels through the body and returns to its starting point in a single circuit (loop)

double circulation

circulatory systems that have two circuits of blood flow (amphibians, reptiles, and mammals)

partial pressure

the pressure exerted by a particular gas in a mixture of gases

ventilation

movement of the respiratory medium over the respiratory surface that maintains the partial pressure gradients of oxygen and carbon dioxide across the gill that are necessary for gas exchange

countercurrent exchange

the exchange of a substance or heat between two fluids flowing in opposite directions

tracheal system

a network of air tubes that branch throughout the body.

larynx

the upper part of the respiratory tract that moves upward and tips the epiglottis over the glottis, which is the opening of the windpipe. This allows food to go down the esophagus to the stomach

alveoli

air sacs clustered at the tips of the tiniest bronchioles. Gas exchange in mammals occurs in these

surfactant

a mixture of phospholipids and proteins that coats the alveoli and reduces surface tension

positive pressure breathing

ventilating the lungs by inflating them with forced air-flow

negative pressure breathing

mammals employ this by pulling, rather than pushing, air into their lungs. Using muscle contraction to actively expand the thoracic cavity, mammals lower air pressure in their lungs below that of the air outside their body.

metabolism

the totality of an organism’s chemical reactions. This is an emergent property of life that arises from orderly interactions between molecules.

metabolic pathway

begins with a specific molecule, which is then altered in a series of defined steps, resulting in a certain product.

catabolic pathways

degradative processes called breakdown pathways

anabolic pathways

consume energy to build complicated molecules from simpler ones

energy

capacity to cause change

kinetic energy

energy associated with the relative motion of objects