IX. Anatomy
Key focus of this chapter: 4 types of tissues
This chapter focuses 4 types of tissues and gives concise summaries of the important things about glands in tissue cells, skeletal muscles, bone, ear, and eye.
A. Tissues
: groups of similar cells organized to work a common function.
1. Four types of tissues
a. Epithelial
: covering the outside of the body and the external or internal surfaces of organs for secretion, absorption, and protection.
- Simple epithelium is single layer and stratified epithelium is two or more layers.
- Cuboidal epithelium is cube shaped and squamous epithelia is flat.
b. Connective
: functions to transport, support, connect, and protect the other three kinds of tissue.
- Types – cartilage, bone, and blood
c. Muscle
: contains contractile muscle fibers and function for movement.
- Types – smooth muscle, skeletal muscle, and cardiac muscle
d. Nerve
: transmission of electrical information to central and peripheral nervous system.
- Types – spinal cord tissues, brain
- Grey matter (information processing) and white matter (information transmission)
2. Features and functions of each tissue
Tissues | Classification | Shapes | Features and functions |
Epithelial | Cuboidal epithelia |  | • Cube shape • Specialized for glands, secretion |
Columnar epithelia |  | • Column and elongated shapes • Lining of intestine and stomach for secreting digestive enzymes and absorbing nutrients | |
Squamous epithelia |  | • Flat shape • Lining and cover of lungs for exchanging gases and diffusion of nutrients | |
Connective | Cartilage |  | • Covers skeletal joint, outer ear, nose, larynx, trachea, bronchial tubes • Chondrocytes – secrete collagen and chondroitin sulfate to absorb physical impact • Avascular form |
Bone |  | • Supports body of vertebrates • Osteocytes – bone cells • Provides rigidity and hardness by calcium, phosphate, magnesium ions | |
Blood |  | • Platelets – clotting aid • Leukocytes – white blood cells, immunity aid • Plasma – liquid matrix • Erythrocytes – red blood cells, carry oxygen, lack nuclei | |
Fibrous connective tissue |  | • Tendon - connects bone to muscle (origin is connection of stationary bone to muscle and insertion is connection of moveable bone to muscle) • Ligaments – connects bone to bone | |
Muscle | Skeletal muscle |  | • Voluntary and striated muscle • Array of actin and myosin filaments with multiple nuclei • Sarcomeres – contractile units • Myofibrils fibers |
Cardiac muscle |  | • Found in wall of heart • Involuntary and striated muscle • Branched cells • Intercalated discs -interconnects the signaling of heartbeats between the end of cells | |
Smooth muscle |  | • Found in digestive tract, arteries, urinary bladder • Involuntary and not striated muscle • Thin and elongated cells with spindle shape |
B. Glands in tissue cells
1. Exocrine gland
- Secrete their products via duct to external environment
- Eg/ Sweat gland, mammary gland, salivary gland
2. Endocrine gland
- Secrete their products into capillaries in the internal environment
- Eg/ Adrenal gland, pituitary gland, thyroid gland
** Sweat gland and capillaries function for thermoregulation
C. Skeletal muscles
1. Structure of skeletal muscle
a. Sliding filament model of muscle contraction
- Myofibril contains repeated sarcomeres.
- During muscle contraction, the actin (thin filament) and the myosin (thick filament) overlap each other.
- Myosin is linked by M line and actin is linked by Z line.
- During muscle contraction, the width of I band and H zone are reduced but the width of A band is not changed.
b. Process of the contraction of a skeletal muscle fiber
- ① Acetylcholine (ACh) is released from synaptic terminal of motor neuron.
- ② Acetylcholine (ACh) is bound to ACh receptors on muscle fiber’s plasma membrane.
- ③ Action potential spreads along sarcolemma and goes down T tubules.
- ④ Action potential launches Ca2+ from sarcoplasmic reticulum (SR) to troponin
- ⑤ Ca2+ binds to troponin.
- ⑥ Myosin cross-bridge alternately contacts and detaches to actin, then muscle fiber contracts.
- ⑦ Ca2+ is removed from troponin and back to sarcoplasmic reticulum (SR) when action potential ends, then muscle fiber relaxes.
2. Neural control
a. Tetanus
: continuous muscular contraction
– summation of tension
– the higher frequencies of stimulation leads muscle fibers to a state of tetanus sustained contraction.
- Motor unit – many muscle fibers are controlled by one motor unit.
- Twitch – mechanical response of muscle fibers from stimulation.
- Tonus – partial contraction of muscle during resting state.
b. Isometric and isotonic muscle contractions
- Isometric muscle contraction – force generates with the constant length of the muscle
- Isotonic muscle contraction – force does not generate with the shortened length of the muscle
D. Bone
1. Functions
- Making blood cells
- Framework for movement
- Protection of organs
2. Bones of human skeleton
- Axial skeleton
– skull, vertebra, sternum, rib
- Appendicular skeleton
– arm bones: humerus, radius, ulna
– hand bones: carpals, phalanges, metacarpals
– leg bones: femur, patella, tibia, fibula
– food bone: Tarsals, metatarsals, phalanges
3. Structure of bone
Classification | Functions and features |
Osteoclast | • Breaks down bone by releasing calcium |
Osteoblast | • Makes bone by deposition of calcium |
Osteocyte | • Immobilizes bone and transformed by osteoblast |
Haversian canal | • Covers blood vessels and nerves and communicate with osteocytes |
Epiphyseal plates | • The region of bone growth at the ends of long bones |
E. Eye
1. Structure of eye
a. Outer ear
- Collects outside sounds
- Consists of pinna and auditory canal
b. Middle ear (ossicles)
- Functions as amplifying primary sound energy
- Consists of three small bone – malleus, incus, stapes
c. Inner ear
- Fluid – filled chambers
- Consists of semicircular canals and cochlea
Classification | Functions and features | |
Outer ear | Pinna | • Collecting sound |
Auditory canal | • Transmission of sound to tympanic membrane | |
Tympanic membrane | • Ear drum • Dividing outer ear from middle ear • Transmission of sound to middle ear | |
Middle ear (ossicles) | Malleus | • Hammer shaped small bone |
Incus | • Anvil shaped small bone | |
Stapes | • Stirrup shaped small bone | |
Inner ear | Semicircular canals | • Three half circular canals • Sensor for equilibrium of body |
Cochlea | • Distinguishes the different vibrations of sound and sends these signals to auditory nerve | |
Auditory nerve | • Transmission of sound signals to brain | |
2. Processing sound information
F. Eye
1. Structure of eye
Classification | Functions and features |
Sclera | • Consists of white and tough outer layer of eye |
Cornea | • Front part of sclera and fixing lens • Passes and initial focusing of light |
Choroid | • Inner pigmented vascular layer |
Retina | • Photoreceptor tissues and innermost layer |
Iris | • Controls the amount of light by regulating pupil size |
Pupil | • Center of iris and hole of light |
Lens | • Focuses light on the retina |
Aqueous humor | • Watery matter and anterior cavity |
Vitreous humor | • Jellylike matter and posterior cavity |
Optic disk | • No sensitivity to light (blind spot) • Connecting to optic nerve |
2. Light response in retina
a. Rod and cone cells
- Rod cells – sensitivity of black and white in less intense light
- Cone cells – sensitivity of colors in strong intense light
b. Light and dark responses
- Response in light
– active rhodopsin
– close Na+ channels
– rod and cone cells are hyperpolized
– no glutamine secreted
- Response in dark
– inactive rhodopsin
– open Na+ channels
– rod and cone cells are depolarized
– glutamine secreted