Solve these clues to fill the grid.
- That part of the central nervous system that includes all the higher nervous centers
- 3 Across
- Any chamber that is connected to other chambers or passageways
- 5 Across
- Rigid connective tissue that makes up the skeleton of vertebrates (plural)
- 7 Across
- The outer layer of the skin covering the exterior body surface of vertebrates
- 8 Across
- Red liquid pumped around the body by the heart
- 9 Across
- A ___ that contracts without conscious control and found in walls of internal organs such
- 11 Across
- The longest and thickest bone of the human skeleton
- 13 Across
- Either of two saclike respiratory organs in the chest of vertebrates (plural)
- 14 Across
- Either of two large veins that return oxygen-depleted blood to the right atrium of the heart
- 15 Across
- Either of two bean-shaped excretory organs that filter wastes from the blood and excrete them
- 16 Across
- A natural protective body covering and site of the sense of touch
- 1 Down
- Tough elastic tissue
- 2 Down
- Any substance that promotes ___
- 4 Down
- A chamber of the heart that receives blood from an atrium and pumps it to the arteries
- 6 Down
- Of or relating to or near the part of the back between the ribs and the hipbones
- 10 Down
- One of the contractile organs of the body
- 12 Down