Physical & Health Education · Lesson 2

Cells, skeleton, muscles, nervous system and senses, circulation, respiration, body types and posture

JAMBWAECNECO

What the syllabus asks

JAMB: cells, tissues and systems; skeletal; muscular; nervous system and sense organs; circulatory; respiratory; excretory; somatotypes and posture)

WAEC: anatomy and physiology of the human body

NECO: anatomy and physiology of the human body

What you will learn

Describe the structure and functions of a typical human cell and the four tissues.
Distinguish mitosis from meiosis and explain differentiation.
Name the bones of the axial and appendicular skeleton and state the functions of the skeleton.
Describe bone structure, bone types, joint types and joint movements.
Name major muscles, their actions and types of contraction.
Describe the nervous system, reflex action and the sense organs.
Explain the heart, blood vessels, blood and double circulation.
Explain breathing, respiration and excretion.
Describe somatotypes, correct posture and postural defects with causes and corrections.

Key points

Cell parts: membrane, cytoplasm, nucleus, mitochondria, ribosomes; no cell wall in human cells.
Tissues: epithelial, connective, muscle, nervous; tendons (muscle–bone), ligaments (bone–bone).
Mitosis (growth/repair, 2 cells, 46) vs meiosis (gametes, 4 cells, 23).
206 bones; axial 80, appendicular 126; femur longest; spine 7-12-5.
Skeleton functions: support, protection, movement, blood cell formation, mineral store.
Bone types: long, short, flat, irregular, sesamoid.
Joints: fibrous, cartilaginous, synovial; six synovial types; flexion, extension, abduction, adduction, rotation, circumduction.
Muscle: skeletal, smooth, cardiac; agonist/antagonist; concentric, eccentric, isometric.
Nervous system: CNS/PNS; cerebrum, cerebellum, medulla; reflex arc.
Sense organs: eye, ear (cochlea hearing, semicircular canals balance), nose, tongue, skin.
Heart: 4 chambers, double circulation; arteries, veins, capillaries; plasma, RBC, WBC, platelets.
Breathing by diaphragm and intercostals; aerobic vs anaerobic; excretion by kidney, skin, lungs; somatotypes and posture.

Start here: The cell: structure and functions

All living things are made of cells, the smallest units that can carry out life processes. An adult human body contains trillions of cells, and every movement you make on the football pitch begins with chemical reactions inside them. Anatomy is the study of the structure of the body; physiology is the study of how it works. PHE examiners test both, always with an eye on exercise.

Parts of a typical human cell

Cell (plasma) membrane: a thin, flexible outer layer of fat and protein. It is selectively permeable: it lets oxygen, glucose and water in and lets carbon dioxide and wastes out.
Cytoplasm: jelly-like fluid where most chemical reactions take place and where organelles float.
Nucleus: contains the genetic material (DNA in chromosomes) and controls the cell’s activities and division. Inside it is the nucleolus, which makes ribosomes.
Mitochondria: the “power stations”. Aerobic respiration here releases energy stored as ATP. Muscle cells of trained endurance athletes have more and larger mitochondria, one reason a long-distance runner from the Jos plateau can run for hours.
Ribosomes: make proteins, including the contractile proteins actin and myosin in muscle.
Endoplasmic reticulum (transport network), Golgi apparatus (packages and secretes), lysosomes (digest worn-out parts).

Human (animal) cells have no cell wall, no chloroplasts and no large permanent vacuole; plant cells have all three. This difference is a favourite one-mark question.

Functions of cells in the body

Cells grow, divide to repair injuries (think of a grazed knee healing after a fall on the volleyball court), make substances (hormones, enzymes), carry messages (nerve cells), contract (muscle cells) and transport gases (red blood cells).

Worked example 2.1 (JAMB style)

The organelle responsible for releasing energy in a muscle cell is the (A) nucleus (B) ribosome (C) mitochondrion (D) cell membrane. Answer: C. Aerobic respiration in mitochondria produces ATP, the energy currency used for contraction.

Worked example 2.2 (WAEC essay)

List four parts of an animal cell and state one function of each. Model answer: membrane – controls entry and exit of substances; nucleus – controls cell activities and carries genes; mitochondrion – releases energy; cytoplasm – site of chemical reactions. Four parts with correct functions = 4 × 2 marks.

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Practice questions

1. The axial skeleton has

80 bones
126 bones
206 bones
33 bones

Show answer

A: 80 bones
Appendicular 126; total 206.

2. The total number of bones in the adult human skeleton is

Show answer

D: 206
80 axial + 126 appendicular.

3. How many cervical vertebrae are there?

Show answer

C: 7
Then 12 thoracic and 5 lumbar.

4. A bone found inside a tendon, such as the patella, is a

short bone
sesamoid bone
long bone
flat bone

Show answer

B: sesamoid bone
It sits in the quadriceps tendon.

5. Bending a joint to decrease the angle between bones is

flexion
extension
abduction
rotation

Show answer

A: flexion
Extension increases the angle.

Key words

Anatomy: Study of body structure.
Physiology: Study of how the body works.
Tissue: Group of similar cells doing one job.
Mitosis: Cell division producing two identical diploid cells.
Meiosis: Cell division producing four haploid gametes.
Axial skeleton: Skull, spine, ribs and sternum (80 bones).
Appendicular skeleton: Limbs and girdles (126 bones).
Ligament: Tissue joining bone to bone.
Tendon: Tissue joining muscle to bone.
Synovial fluid: Lubricating fluid in freely movable joints.
Agonist: Prime mover muscle.
Antagonist: Muscle that relaxes to allow movement.

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