1. Introduction to Body Structure
Ch. 38
Biology
Ms. Haut

2. Levels of Structural Organization
Cell—smallest functional unit
Tissue—group of similar cells performing a common function
Organ—combination of 2 or more tissues that work together
Organ system—combination of 2 or more organs working together to perform a common function

3. Epithelial Tissue Lines most body surfaces—inside and out
Protects other tissues from dehydration and physical damage

4. Nervous Tissue Consists of nerve cells (neurons)
Carries messages throughout the body

5. Connective Tissue Support, protect, and insulate the body Fat
Cartilage
Bone
Tendons
blood

6. Muscle Tissue Skeletal Smooth Cardiac
Voluntary—can control contractions
Moves bones in trunk and limbs
Smooth
Involuntary—can’t control contractions
Slow, long-lasting contractions
Line blood vessels and digestive tract
Cardiac
Involuntary
Found only in the heart

7. Skeletal Muscle

8. Smooth Muscle

9. Cardiac Muscle

10. Body Cavities House and protect major internal organs
Organs suspended in fluid that supports their weight

11. Endothermy Mammals are endothermic
Have ability to maintain a constant internal body temperature
Humans maintain a body temp. of 38C (99F )
The body uses a lot of energy to maintain a stable internal condition (homeostasis)

12. Skeletal System Functions to support the body Two Main Parts
Axial skeleton
Bones of the skull, spine, ribs, and sternum
Appendicular skeleton
Forms the appendages (limbs)
Bones of the arms, legs, pelvis, and shoulder

13. Bone Structure

14. Bone Growth
In early development the skeleton is made mostly of cartilage
Serves as template for bone formation
Cartilage is gradually replaced by bone as calcium and minerals are deposited
New bone cells (osteocytes) are added in layers around hollow channels (Haversian canals) which contain blood vessels

15. Compact Bone
Concentric rings of bone surround the Haversian canals

16. Longitudinal Growth occurs along the Growth Plate in Bones

18. Importance of Calcium: Got Milk?
Almost all of the body's calcium (99%) is present in the bones and teeth. The remaining 1% is found in the blood and some nerve cells
The amount of calcium in the blood must remain at a steady level
If your calcium intake is inadequate, the body uses the 'stored' bone calcium to maintain the blood calcium.
This mobilization of bone calcium can lead to osteoporosis, i.e., a reduction in the amount of calcium in the bone leading to weak and thin bones.

20. Joints Fasten Bones Together
Pads of cartilage cushion the ends of the bones of a joint
Bones of a joint are held together by ligaments (connective tissue)

23. Muscular System Skeletal muscles move the body
Muscles are attached to bones by tendons
Muscles typically work in opposing pairs

24. Opposing Muscle Pairs

25. Muscles Move Skeletal Parts
Skeletal Muscle
Each muscle fiber is a single cell with many nuclei
Each fiber is composed of a bundle of myofibrils which contain myofilaments
Thin filaments—actin
Thick filaments—myosin
Striated appearance due to sarcomeres (basic functional unit)

26. Muscle Contractions: “Sliding-Filament Model”
Thin and thick filaments of the sarcomere slide past one another to shorten the length of the muscle

27. Cyclic Interaction Between Actin and Myosin in Muscle Contraction

28. Sliding-Filament Model

29. Integumentary System Skin, hair, and nails
Skin is the largest organ of the body
Protects the body from injury
Provides 1st line of defense against disease

30. Skin has 2 Distinct Layers
Epidermis
Outermost layer
Made up of several layers of epithelial cells
Flattened, dead cells that contain keratin (protein that waterproofs skin)
Damaged cells replaced by cells below
Inner layer contains melanin—absorbs UV radiation

31. Skin has 2 Distinct Layers
Dermis
Functional layer of skin
Presence of connective tissue makes it tough and elastic
Contains nerve cells, blood vessels, and hair follicles
Nerve cells sense temperature and pain
Blood vessels responsible for regulating temperature
Sweat glands—evaporation of sweat from skin cools body

32. Acne
Chronic inflammatory condition that involves the skin’s oil-producing glands
Oil glands release sebum (oily secretion that lubricates the skin)
Released through ducts (exocrine glands)
Acne results from the duct pores being clogged with oil, dirt, and bacteria
Surrounding tissue gets infected and inflamed, and pores accumulate pus, producing pimples

33. Skin Cancer
Results from genetic mutations from overexposure to UV radiation
Carcinoma—originates in cells without melanin
Can be treated early on
Malignant melanoma—mutation occurs in melanin producing cells
Grow quickly and spread easily