Human Growth and Development PDF

# Definitions - **Growth:** the normal increase in amount of living organism - It is **quantitative** aspect - measured in terms of increments - **Development:** increase in skills and function (the ability of a child of doing things that are complex and difficult) - Progress toward matu...

# Definitions - **Growth:** the normal increase in amount of living organism - It is **quantitative** aspect - measured in terms of increments - **Development:** increase in skills and function (the ability of a child of doing things that are complex and difficult) - Progress toward maturity - **Maturation:** All normal sequential series of events between fertilization of ovum and the adult (maturation state) - It's **qualitative** (refers to increase in complexity of tissues) - It is **immeasurable** - **Growth increment:** the amount of growth per unit time (growth/time) - **Growth spurt:** the sudden increase in growth rate ## Growth spurts - **Infantile growth spurt:** 2 y - **Juvenile growth spurt:** 9 y - **Pubertal / adolescent growth spurts:** 11 to 13 in girls, 13 to 15 in boys ## Differential growth - **Differential growth:** difference in growth rate and time of various organs of the organism. - **Examples of differential growth:** - Cephalo-caudal gradient - Scammon's growth curves ### Cephalo-caudal gradient of growth - The axis of increased growth shifts from head to the lower extremities as a child grows into an adult. - At birth the face length is 1/4 the whole body length while at adult it is 1/8 the whole body. ### Scammon's growth curves - **Somatic (general) growth:** (maxilla, mandible, skull) - The increase in overall body size throughout growth period continues. - Rapid in 1st months after birth. - Slowly declines till the pubertal growth spurt. - Pubertal growth spurt (when?) - Declines to reach zero by about 20 years. - **Neural growth:** - C.N.S grows rapidly prenatally and early postnatally. - The human brain attains 90% of its full adult size by 6 years although its functional maturation continues for a longer time. - No pubertal growth spurt - **Lymphatic growth:** - The lymphatic tissues grow rapidly in early life and reach their maximum (200% of its full size) at about 11-14 years after which they decline. - **Genital growth:** - The primary and secondary sexual organs remain small until puberty then they grow to adult size. # Bone formation (Osteogenesis) (Ossification) - Bone is formed in 2 connective tissue sites: - cartilage - membranous connective tissue - This leads to two paths of bone development: ## Endochondral bone formation: - Original mesenchymal tissues first become cartilage cell. - Cartilage cells hypertrophy / hyperplasia. - Their matrix become calcified. - Cells degenerate. - Replacement by osteogenic tissue. - Bone - **Examples of Endochondral bone formation:** - Epiphyseal plates (knee) - Nasal cartilage - Condylar cartilage - Synchondroses (cranial base) - Symphyseal cartilage (close by one year) ### Synchondroses - The bones of the cranial base are formed by endochondral ossification. - Bands of cartilage called Synchondroses remain between different bones. - **Sphenoid-occipital synchondrosis:** between the sphenoid and occipital bones. Major contributing in the postnatal growth. - It closes at 18-20 years (closed a few years earlier in girls than boys) - **Spheno-ethmoidal synchondrosis:** - It exists between the sphenoid and ethmoid bones. - It closes at about 5-7 years. - **The intra-occipital synchondrosis:** - It is present inside the occipital bone. - It closes at 3-5 years. - **The intersphenoidal synchondrosis:** - It exists between 2 parts of the sphenoid bone. - It closes just before birth. ## Intramembranous bone formation: (appositional and additive in nature or sutural) 1. UMCs (Undifferentiated Mesenchymal Cells) change to Osteoblasts that elaborates Osteoid matrix. 2. The entrapped osteoblast changes to osteocytes. 3. Matrix calcified by osteocytes. 4. Bone - **Example:** bone tissue is laid down by: - Periodontal ligament - Sutures - Bone of clavarium (cranial vault) - Periostium - Endosteum ### Sutures - Periosteal membrane between the edges of adjacent bones. - **Surface deposition:** - Pressure from the growing brain promotes resorption of the inner surfaces. - Deposition on external surface. - Remodeling & the cranial bones become thicker. - This increase in thickness is not uniform. # Theories Regarding Growth 1. **The Classical Theory (Sicher's):** Inaccurate - The proliferation of the soft tissues in the suture separate the bones bounding it, (build in). - Suture is considered as a growth center. 2. **The Functional Matrix Theory (Moss):** Accurate - Separation of bones at sutures is produced by growth of another organ e.g. the brain, eyeball, cartilage at the synchondrosis or the nasal cartilage. - Soft tissue adjacent to bone is the primary determinant of growth while suture's response is secondary. | Growth center (growth initiator) | Growth site (growth adjuster) | Location of growth | |---|---|---| | Build in | Fill in | | | Endochondral ossification with tissue separating force occurs | where periosteal or sutural bone is formed in adaptation to environmental influences | | | **a) cartilage** 1. Synchondrosis 2. Nasal cartilage 3. Epiphyseal plates | **b) soft tissue** 4. expansion of a soft tissue organ occurs that leads to growth of the neighboring skeletal structures. Eg. Brain / eye | cranial vault. (Sutures) | | # Growth movements (concepts) - During enlargement of the craniofacial bones, 2 kinds of growth movements occur - Drift - Displacement - Primary displacement - Secondary displacement - **Drift (cortical drift) (Relocation):** - Movement of bone in the same direction of its own growth - Combination of bone resorption and deposition - Growth movement towards the deposition side - It's produced by the deposition of bone on one side of the cortical plate while resorption occurs on the opposite side. - **Example:** Ramus and palate - **Displacement:** - Movement of the whole bone as a unit. - **Primary displacement:** movement of bone in opposite direction to its own growth. - **Examples:** - Sutural growth - growth at the mandibular condyles (body of mandible) - forward displacement of maxilla by bone deposition in the maxillary tuberosity area posteriorly. - **Secondary displacement:** movement of bone in the same direction of growth of other adjacent or distant bone. - **Example:** displacement of the naso-maxillary complex (secondary) to the cranial base (maxilla in relation to the brain) - **Remodeling:** the change in size and shape of bone as a result of differential resorption and deposition of the inner and outer surfaces. - **Example:** (mandibular angle) # The Craniofacial Complex ## I - The Cranial Vault - Consist of frontal, parietal, temporal and occipital bones which are joined together at the sutures. | Type of growth | Growth in Width | Growth in Length | |---|---|---| | Intramembranous (Sutural Growth) & Surface Deposition | 1. Metopic Suture 2. Mid Sagittal Suture | 1. Coronal Suture 2. lambdoidal suture | ## II - The Cranial Base - The cranial base grows primarily by cartilaginous ( endochondral) growth in the synchondroses - When the cranial base grows anteroposteriorly, this brings NMC downward and forward (2ry displacement) - The increase in length of cranial base give chance for NMC & alveolar region to grow vertically - **Spheno-Occipital Synchondrosis** - Ant to TMJ & post to ant cranial fossa "sella tarcica" - Its growth influences the overall facial skeletal pattern. - It persists to 18-20 years of age closing a few years earlier in girls. ## III - The Nasomaxillary complex - The middle face consists of orbits, zygomatic bone, nasal cavity, paranasal sinuses, alveolar process and palate. - The middle face expands in width, depth and height (the most remarkable). - Growth in width, then depth and finally height respectively. | Growth in Height | Growth of Face in Width | Growth in Antro-posterior (depth) | |---|---|---| | 1. 1ry displacement at nasal cartilage 2. 2ry displacement at synchondrosis "brain" 3. Drift at palate 4. Alveolar growth | 1. Sutural growth at median palatine raphe 2. Bone is deposited to the lateral walls of: orbits, the nasal walls, maxillary sinuses, zygomatic arches and lateral maxillary surface. 3. Eye suture 4. growth of alveolar bove | 1) 1ry displacement at nasal cartilage & tuberosity 2) 2ry displacement at synchondrosis "prain" 3) sutural growth through: i. Fronto-nasal ii. Fronto-maxillary iii. Zygomatico-maxillary iv. Zygomatico-temporal v. Pterygo-palatine sutures | - The vertical growth of the naso maxillary complex in a downward and forward direction. - Maxillary complex grows both by outward and downward. | | | | |---|---|---| | *Height* | *1/4 face lengt4→ 1/8 after puberty* | *1/4* | | *Gonial angle* | *179° → 115* | *179°* | | *Face 1/8* | *Adult* | *1/8* | | *Need to face VA* | *Adult* | *1/8* | | *Open sutures* | *Child* | *1/8* | | *Closed sutures* | *Adult* | *1/8* | | *Face to cranium* | *1/8* | *1/8* | | *Gonial angle* | *175* | *115* | | *Alveolar bone* | *Absent* | *Present* | # Max. complex Grows by both 1-Enochondralossification at synchondrosis & nasal cartilage 2-Intra-membranous at sutures & surface deposition ## VI- The Mandible. - **Endochondral at condyle and symphysis** - **Intramembranous at the rest of it** - Of the facial bones, the mandible undergoes the largest amount of growth postnatally. ### At birth - Ramus was short - Condyle and coronoid process were underdeveloped - Gonial angel 175 which will be 115 after - Alveolar process was absent ### A) The condyles - Grows in backward and upward direction by endochondral growth. - The concept of growth is primary displacement. - Complete ossification at 20 years. ### B) The Ramus - The posterior border of ramus grows backward by progressive addition of bone - It grows vertically to accommodate the marked downward growth of the NMC and eruption of teeth ### C) Coronoid process - Drift in posterior direction (less than the ramus) # The V principle - Many facial bones or parts of bone show a V type growth pattern & best illustrated by ramus and palate and coronoid - Increase in overall dimension by: - Bone deposition on the inner side of the V. - Bone resorption on the outer surface of the V. - **The body of the mandible:** - **Superior border:** alveolar bone growth - **Inferior border:** bone deposition except antigonial notch - **Outer surface:** bone deposition - **Inner surface:** bone resorption except the mylohyoid ridge - **The alveolar process:** - In case of absence of teeth, alveolar bone fails to develop and it resorbs by tooth extraction. - As the teeth erupt in the alveolar process develops. - **Upward:** increase in height - **Outward:** increase in width (thickness of the mandible) | Growth in width | Growth in length | Growth in height | |---|---|---| | 1) Symphysis cartilage 2) V principle of coronoid process 3) Alveolar growth outward "lat." | 1) Drift in ramus 2) 1ry displacement in body | 1) 1ry displacement to condylar growth 2) Alveolar growth Upward or downward | # Clinical application of growth - **The effect of growth on orthodontic treatment:** - Timing is best related to the various growth spurts. - **Bjork classified these spurts into:** - Infantile: preventive measures - Juvenile: interceptive - Pubertal: Growth modification - Post pubertal: orthodontic treatment (corrective) - Tooth movement is more rapid and stable during the growth period especially when it was at the same direction of growth. ### The effect of orthodontic treatment on growth - **Growth modification by:** - Restraining the growth in maxilla and mandible. - Stimulating and redirection of growth in maxilla and mandible. | | | |---|---| | Reverse head gear | Face mask (deficient maxilla) | | Chin cup (excess mandible) | Twin block (deficient mandible) | | | Head gear (excess maxilla) | - **Class II:** - Max. excess: head gear - Mand. deficient: twin black - **Class III:** - Max. deficient: Face mask "Reverse head gear" - Mand. excess: chin cup - **Andrew's 6 keys of normal occ:** - **1. Correct Molar relation ship:** MB cusp of MB (Ant.) groove. f - ML cuspon central. R - DMRof on MyRof fossa. - **2. Crown angulation:** MD tip "Root distal to crown" tve for all teetti. Movement of crown - Post ling to crown tve. - **3. Crown inclination "BL torque":** (-ve for all teeth exc. central lat." Movement entofi of root. - Root Buccal to crown - **4. Absence of rotation:** incisor rotated less spave. Molar rotated elurespace "Past" - **5. Tight contact** - **6. flat occ plane "curve of spee":** deep crowding in upper, spacing in lower. - Reversed → in lower , in upper.